Resolving WinCC DataMonitor .NET and Web Configurator Errors

WinCC DataMonitor is the Siemens web-based client package for the WinCC SCADA system. It publishes process values, alarms, archives, trends, and screens to Internet Explorer clients using ASP pages, the WinCC Web Configurator, and the Microsoft IIS (Internet Information Services) runtime. When the DataMonitor launch page returns an exception, fails to load the activex or .asp page, or the entire web front end does not respond, the root cause is almost always one of four items: (1) a corrupted or partially installed .NET Framework stack, (2) a missing or disabled Internet Explorer configuration, (3) an incorrect Web Configurator selection, or (4) a host-name / URL binding problem on the IIS site. This reference collects the verified field procedures that resolve each of these classes of error for WinCC DataMonitor V7.0 and newer.

1. Problem Description and Scope

The error pattern reported in the field is consistent across multiple WinCC DataMonitor installations: the user enters the DataMonitor server name (or IP address) in the URL bar of Internet Explorer, presses Enter, and the browser returns an unhandled .NET exception, a blank page, or an HTTP 500-class error referencing the DataMonitor virtual directory. The exception is raised before any WinCC process picture or trend chart is rendered. The browser never reaches the WinCC WebUX splash screen and the WinCC WebNavigator runtime on the server reports no connected client.

This class of fault is independent of the underlying WinCC project. The same WinCC runtime that functions correctly in WinCC Explorer and on locally installed WinCC clients fails to publish to the DataMonitor web front end. Because the failure occurs at the IIS / ASP.NET boundary and not at the WinCC application boundary, the issue must be diagnosed and corrected at the operating-system and web-server layer.

2. Error Symptoms Catalog

Use this symptom matrix to triage the fault before changing the host configuration. The error message in column 1 is the literal text reported by the browser, the .NET runtime, or the WinCC diagnostics viewer.

3. Root Cause: .NET Framework Conflicts

WinCC DataMonitor V7.0 to V7.4 depends on the Microsoft .NET Framework 2.0/3.0/3.5 family. WinCC DataMonitor V7.5 and TIA Portal-based V15-V18 DataMonitor require .NET Framework 4.6.2 or higher. When multiple .NET Framework versions are installed on the same server, and a partial Windows Update or third-party installer has removed a shared assembly from the Global Assembly Cache (GAC), the WinCC .asp pages cannot resolve the DataMonitor namespace and throw a System.IO.FileNotFoundException or a System.TypeLoadException at the first reference to CCDataMonitorCtrl.

The classic field pattern is the user has attempted to clean the .NET installation manually (uninstalling a higher version first) and has broken the chain of shared dependencies. The recovery is to repair the entire .NET stack in the documented order, not to remove or downgrade components.

3.1 Required .NET Version by WinCC DataMonitor Release

4. Root Cause: Internet Explorer Configuration

WinCC DataMonitor V7.x uses Microsoft ActiveX controls (the WinCC WebNavigator Control and the WinCC DataMonitor Control). Only Internet Explorer 9 through 11 supports these controls out of the box. Edge in IE Mode, Edge Chromium, Chrome, and Firefox cannot load the ActiveX runtime, and DataMonitor will fail to start or will present a placeholder window. The browser must be configured to:

1. Add the DataMonitor server URL to the Trusted sites zone (or Local intranet zone if the server is in the same AD domain).
2. Disable ActiveX filtering for the Trusted sites zone (gear icon → Safety → ActiveX Filtering).
3. Enable Initialize and script ActiveX controls not marked as safe for the Trusted zone (Internet Options → Security → Custom level).
4. Disable Enable Protected Mode for the Trusted zone (required for legacy ActiveX signing chain).
5. Ensure the Enhanced Security Configuration (ESC) is disabled for administrators on Windows Server 2008 R2 and 2012 R2 hosts. ESC is removed in Server 2016+ but must be turned off manually on older hosts.
6. Enable the Binary and script behaviors ActiveX control, required for the DataMonitor print/PDF export feature.

5. Root Cause: Web Configurator and ASP Deployment

The WinCC Web Configurator is the tool that registers the DataMonitor IIS site, copies the .asp templates, creates the DataMonitor virtual directory under Default Web Site, and sets the IIS application pool. If the Web Configurator is not run, or is run against an IIS instance that is not yet installed, the virtual directory is missing and IIS returns HTTP 404 for http://<server>/DataMonitor.

Inside the Web Configurator, the operator must select a *.asp template that matches the intended DataMonitor mode. The three templates are:

If the operator selects WinCC Web Navigator by accident but the license and project are configured for DataMonitor, the WebNav.aspx page will load but the DataMonitor-specific namespaces will be absent and the page will throw a runtime exception as soon as the trend or alarm overview is requested. Always re-run the Web Configurator with the correct selection before troubleshooting further.

6. Step-by-Step Resolution Procedure

Execute the following steps in the order given. Each step is independently verifiable; do not skip to step 8 if step 3 fails.

6.1 Verify and Repair the .NET Framework Stack

1. Open Control Panel → Programs and Features and list all installed .NET Framework versions. The version number and the corresponding release update are shown in the Installed Updates column for each KB entry.
2. For DataMonitor V7.0-V7.4, confirm that .NET 2.0 SP2, .NET 3.0 SP2, and .NET 3.5 SP1 are all present. For V7.5+, confirm .NET 4.6.2 (or higher) is present.
3. If any are missing, do not attempt a manual repair. Use the official Microsoft .NET Framework Repair Guide to download and run the Microsoft .NET Framework Repair Tool. This tool re-registers shared assemblies, restores GAC entries, and resets the ASP.NET ISAPI mappings without requiring a Windows reinstall.
4. Reboot the server after the repair tool completes successfully.
5. Open a command prompt as administrator and run:
   %windir%\Microsoft.NET\Framework64\v2.0.50727\aspnet_regiis.exe -i -enable
   (For V7.5+ substitute the v4.0.30319 folder.) This re-registers ASP.NET with IIS 6/7/8/10.

6.2 Verify the IIS Installation

1. Open Server Manager → Roles → Web Server (IIS) and confirm the following role services are installed:
   • Common HTTP Features → Static Content, Default Document, HTTP Errors, HTTP Redirection
   \li>Application Development → ASP, ASP.NET, ISAPI Extensions, ISAPI Filters, Server-Side Includes
2. Management Tools → IIS Management Console, IIS Management Scripts and Tools, Management Service
3. Open IIS Manager (inetmgr.exe) and expand Default Web Site. The DataMonitor application must be listed. If it is absent, return to step 6.4 and re-run the Web Configurator.
4. Click on Application Pools and confirm the DataMonitorAppPool exists. Right-click → Advanced Settings:
   • .NET CLR Version: v2.0 for V7.0-V7.4 SP1, v4.0 for V7.5+
   • Managed Pipeline Mode: Classic for V7.0-V7.4, Integrated for V7.5+
   • Identity: ApplicationPoolIdentity or a dedicated service account with read access to the WinCC project directory
   • Enable 32-Bit Applications: False (DataMonitor is 64-bit on V7.4+)

6.3 Verify the WinCC Project Configuration

1. Open the WinCC Explorer on the server. Right-click the project name → Properties → tab Web Navigator / DataMonitor.
2. Confirm the Activate Web Navigator and Activate DataMonitor checkboxes are enabled.
3. Verify the port number (default 80 for HTTP, 443 for HTTPS). If the port is non-default, the URL used by the client must include the port suffix, for example http://servername:8080/DataMonitor.
4. Confirm the WinCC Runtime is in active state (the tray icon in the system tray is green, not gray).

6.4 Re-run the WinCC Web Configurator

1. Close IIS Manager and the WinCC Explorer.
2. From the Windows Start menu, launch WinCC Web Configurator (Start → Siemens Automation → WinCC → Web Configurator).
3. On the start screen, click Next. The wizard detects the installed IIS instance. If IIS is not detected, abort and return to step 6.2.
4. Select the WinCC DataMonitor template. Do not select WinCC Web Navigator unless operator-input process pictures are required.
5. Choose Standard configuration unless a custom *.asp template has been deployed to the WinCC project.
6. Click Finish. The wizard copies the DataMonitor .asp files to C:\Inetpub\wwwroot\DataMonitor and registers the virtual directory. A successful run closes silently and writes a log entry to C:\ProgramData\Siemens\Automation\WinCC\WebConfigurator.log.
7. Open IIS Manager and confirm the DataMonitor application is present and bound to the correct application pool.

6.5 Configure the Internet Explorer Client

1. On the client machine, open Internet Explorer 11. Add the DataMonitor server URL to the Trusted sites zone.
2. In Custom level for the Trusted zone, set:
   • ActiveX controls and plug-ins → Initialize and script ActiveX controls not marked as safe for scripting: Enable (Prompt is also acceptable but will require user confirmation on every page load)
   • ActiveX controls and plug-ins → Run ActiveX controls and plug-ins: Enable
   • ActiveX controls and plug-ins → Script ActiveX controls marked safe for scripting: Enable
   • Scripting → Active scripting: Enable
   • Downloads → File download: Enable
3. Disable ActiveX Filtering for the Trusted zone: Tools → Safety → ActiveX Filtering (must not be checked).
4. Disable Tracking Protection and any third-party ad-blocker extension for the Trusted zone.

6.6 Test the Connection from the Client

1. From the client, open a command prompt and execute ping <servername>. Verify the hostname resolves to the correct IP address. If the hostname does not resolve, add an entry to the client's hosts file (C:\Windows\System32\drivers\etc\hosts) or to the corporate DNS.
2. From the client, open a command prompt and execute telnet <servername> 80 (or the configured port). A blank screen confirms the port is open. If the connection is refused, the Windows Firewall on the server is blocking inbound HTTP. Open Windows Firewall with Advanced Security and create an inbound rule for TCP port 80 (or 443) allowing the server profile.
3. Open Internet Explorer and navigate to http://<servername>/DataMonitor. The WinCC DataMonitor start page should render.

7. Verification Matrix

Each of the following checks must return the expected result before the DataMonitor is declared operational. The matrix maps a verification step to the layer it exercises and the expected output.

8. Related Fault: Data Monitor "Error Reading Input/Output File" on RSLinx Emulate 500

Engineers searching for Data Monitor errors may also encounter a fault generated by the Allen-Bradley RSLinx Data Monitor plugin when it attempts to read the I/O configuration of an RSLogix Emulate 500 chassis. RSLinx sends the SLC Read I/O Configuration CIP service, which the emulator does not implement. The RSLinx log returns the message:

This is not a Siemens WinCC DataMonitor error and is not resolved by the procedures in sections 6.1-6.6. The resolution is documented in the Rockwell Automation Knowledgebase article 21777. The key remediation steps are:

1. Open RSLinx and navigate to Communications → RSWho.
2. Confirm the Emulate 500 driver is configured for the correct virtual backplane.
3. In the Data Monitor plugin, change the Data Source from I/O Image to File, or to a non-emulated 1756 backplane if one is available.
4. If the Emulate 500 driver is not required, remove it from the RSLinx driver list to prevent repeated CIP errors in the RSLinx event log.

9. Field-Proven Caveats and Edge Cases

9.1 Windows Update Re-enables .NET Stub Dependencies

On Windows Server 2012 R2 hosts, the September 2018 cumulative update (KB4457128 and successors) re-enabled the .NET 3.5 stub installer. A subsequent reboot may have set the DataMonitor AppPool to Stopped state because the .NET 3.5 feature was toggled to Not installed. Re-install the .NET 3.5 feature using Add Roles and Features and restart the AppPool. The behavior is documented in Microsoft KB 3005628.

9.2 Self-Signed Certificate Errors on HTTPS Binding

If the DataMonitor site is bound to HTTPS using a self-signed certificate, Internet Explorer will block the page with There is a problem with this website's security certificate. Add the certificate to the Trusted Root Certification Authorities store on the client, or deploy a certificate from the corporate CA. The binding is configured in IIS Manager → Default Web Site → Bindings.

9.3 Firewall Blocks DataMonitor on Distributed Architectures

When the DataMonitor IIS server and the WinCC Runtime server are on different machines, additional firewall rules are required. The DataMonitor client initiates an HTTP(S) request to the IIS host (port 80/443), but the IIS host then opens an RPC connection back to the WinCC Runtime on a dynamic port. Open the WinCC Runtime inbound profile for WinCC Explorer.exe and CCAlgCS.exe in Windows Firewall. Detailed port and process mapping is in the WinCC Communication Manual shipped with the install media.

9.4 Windows Server Core and Nano Server Are Not Supported

WinCC DataMonitor V7.x and V7.5 do not install on Server Core or Nano Server SKUs. The ActiveX and WinCC WebNavigator Control require the full desktop shell. Use Server with Desktop Experience SKU only.

9.5 Microsoft Edge Chromium Compatibility

Microsoft Edge in IE Mode (Edge 77 and newer) can host the WinCC WebNavigator ActiveX for some flows, but the DataMonitor start page uses legacy document.all APIs and a customized ActiveX container that does not render correctly in IE Mode. Use Internet Explorer 11 as the primary client. Plan the migration to WebUX or WinCC Unified (TIA Portal) for browser-agnostic access.

10. Preventive Maintenance Schedule

Repeat the verification matrix in section 7 on a quarterly basis. Track the following items in the CMMS (Computerized Maintenance Management System) for the HMI / SCADA system:

• Monthly: Confirm the DataMonitorAppPool is Started in IIS Manager; confirm the WinCC Runtime is in active state.
• Quarterly: Run the Microsoft .NET Framework Repair Tool to validate the GAC and re-register the ASP.NET ISAPI. Reboot only if a repair action is reported.
• Semi-annually: Update the Internet Explorer Trusted sites list, review ActiveX permission levels, and re-confirm the WinCC Web Configurator selections against the current project license.
• Annually: Apply Siemens WinCC update packages and matching DataMonitor hotfixes. Confirm the .NET Framework version requirement against the updated product matrix in section 3.1.
• On every Windows cumulative update: Verify .NET 3.5 (or 4.x) feature state, the DataMonitor AppPool state, and the integrity of the DataMonitor virtual directory.

11. Frequently Asked Questions