Resolving WinCC WebNavigator "This is no DataMonitor Server" Client Error

The Siemens WinCC WebNavigator client error message "This is no DataMonitor Server - please update the DataMonitor client from a CD" appears when a browser session intended for a WebNavigator server is instead routed to a published DataMonitor endpoint, when client-side runtime components are mismatched, or when Internet Explorer components have been corrupted. This article documents the diagnostic procedure and the four verified field fixes used by automation engineers to restore remote WebNavigator client connectivity against WinCC V7.0 SP3 HF4, WinCC V7.2, and WinCC V7.5 SP2 servers running on Windows 7, Windows XP SP2, and Windows XP SP3.

1. Problem Overview and Field Symptoms

The error surfaces on the WinCC WebNavigator client when one of the following conditions is detected during the initial HTTPS/HTTP handshake between Internet Explorer and the WinCC WebNavigator server:

• The WinCC project is published as DataMonitor Server in the Web Configurator instead of as a WebNavigator Client.
• The local browser cache holds a stale copy of the WebNavigator Client ActiveX control that was originally installed for a different server type.
• A previous DataMonitor client installation is registered with the WinCC web runtime and intercepts the connection request.
• Internet Explorer COM/ActiveX subsystems are corrupted, preventing the proper WebNavigator OCX from registering on first connect.

Observed symptom patterns from the field:

The fact that Windows XP SP2 behaves correctly while Windows XP SP3 and Windows 7 32-bit fail with the same server configuration points to a client-side runtime resolution problem rather than a server-side misconfiguration. The behavior is also VPN-agnostic; field deployments using Cisco VPN Client, Palo Alto GlobalProtect, and Juniper NetworkConnect 7.1.0 have all reproduced the same dialog, which rules out tunnel fragmentation or MTU issues.

2. Affected Versions and Operating Environments

The following combinations have been verified in production deployments and reproduced in lab environments:

The full WinCC V7.5 SP2 server-side behavior is documented in the official Siemens industry support portal entry WinCC Basic Options V7.5 SP2: WebNavigator, DataMonitor, WebUX, which states that "The WebNavigator client is connected with a WebNavigator server operated in WinCC ServiceMode." This is the architectural relationship that drives the failure mode: when the server is published in the wrong mode, the client runtime cannot complete its handshake.

3. Root Cause Analysis

Three independent root causes have been identified. In any given deployment one or more of these may be present, and field fixes typically address all three to ensure a clean return to service.

3.1 Server-Side Publication Mode Mismatch (Primary Cause)

The WinCC Web Configurator (Start > Siemens Automation > Web Configurator) determines which ASP page is served when a client browser connects to the WinCC web root. The valid publication modes are:

If the project is published as a DataMonitor Server but a client attempts a WebNavigator session, the server returns the DataMonitor splash and the WebNavigator client runtime prints the prompt: "This is no DataMonitor Server - please update the DataMonitor client from a CD." This is the same string in WinCC V7.0 SP3 HF4 and WinCC V7.2.

3.2 Stale or Mixed Client Runtime (Secondary Cause)

The WebNavigator Client and the DataMonitor Client both register COM components under HKEY_CLASSES_ROOT\CLSID and both install ActiveX controls into the Internet Explorer Downloaded Programs cache (%LOCALAPPDATA%\Downloaded Installations). A previous DataMonitor installation that has not been cleanly removed will register the wrong TypeLib GUID and the WebNavigator OCX will fail to instantiate. This is the failure mode that the IE9 uninstall + clean reinstall + cache wipe procedure addresses.

3.3 Corrupted Internet Explorer COM Subsystem (Tertiary Cause)

On Windows XP SP3 and Windows 7 32-bit, the IE9 COM subsystem can become corrupted by security patches, antivirus scanning, or partial component updates. When IE9 cannot instantiate WinCCWebNavigatorClient.dll on first contact, the server's automatic client push fails silently and the browser tab falls back to the static splash page, where the DataMonitor dialog is shown.

4. Pre-Diagnostic Checklist

Before applying any of the fixes below, validate the following items. Capturing them now documents the starting state and provides a comparison baseline.

1. Open Internet Explorer on the client PC. Navigate to about:version and record the IE version string and the User Agent.
2. From the command line, run reg query "HKLM\SOFTWARE\Siemens\WinCC\WebNavigator" /s > pre_reg.txt to capture the WebNavigator registration state.
3. Open Control Panel > Programs and Features and list every installed Siemens entry. Specifically confirm whether both WinCC WebNavigator Client and WinCC DataMonitor Client are installed, and record the version of each.
4. On the server, open the WinCC project, launch Web Configurator, and record the current publication mode.
5. Confirm that the WinCC Runtime is running and that the WebNavigator service is started. In services.msc, look for WinCC WebNavigator and WinCC ServiceMode.
6. From the client, attempt http://<server-ip>/WebNavigator/WebClient.asp directly and capture the response. A clean 200 OK with the login dialog is expected; a 302 redirect to the DataMonitor splash confirms the publication mode mismatch.
7. Capture the WinCC project version from the server's \WinCC\ProjectName\<ProjectName>.pdl metadata and the WebNavigator server build from \WinCC\WebNavigator\Server\WinCCWebNavigatorServer.dll File Version property.

5. Solution 1 - Republish the WebNavigator Client in Web Configurator

This is the most common field fix and resolves the error in the majority of WinCC V7.0 SP3 and WinCC V7.2 deployments.

5.1 Procedure on the WinCC Server

1. On the WinCC server, log in with an administrative account.
2. Open Start > All Programs > Siemens Automation > WinCC > Web Configurator.
3. In the Web Configurator main window, select the WinCC project you intend to publish.
4. On the Publishing tab, locate the dropdown "Publish website as" (German: "Website veröffentlichen als").
5. Select WebNavigator Client. If a start picture must be enforced, select WebNavigator Client with start picture (which sets the default ASP to MainControl.asp). Do not select DataMonitor Server.
6. Click Publish (or Finish) to write the new IIS configuration.
7. Restart the WinCC WebNavigator service from services.msc.
8. If the server is operated in WinCC ServiceMode (typical for V7.5 SP2 per Siemens KB 109792604), verify in the WinCC ServiceMode Configuration that the project startup type is Automatic and that the runtime is in Started state.

5.2 Verification on the Client

1. From the client PC, open a fresh Internet Explorer window (no other tabs, InPrivate mode preferred).
2. Clear the browser cache via Tools > Internet Options > General > Delete. Tick Temporary Internet Files, Cookies, History, and Form Data.
3. Navigate to http://<server-ip>/WebNavigator/WebClient.asp.
4. The WinCC login dialog should appear directly, without any DataMonitor splash. Enter the configured WinCC user credentials.
5. After login, the WebNavigator start picture should load within 10-15 seconds. The Picture Tree, Alarm Window, and Trend controls should all populate.

6. Solution 2 - Uninstall the DataMonitor Client and Reinstall the WebNavigator Client

If the publication mode is correct but the client still receives the DataMonitor dialog, a stale DataMonitor installation is hijacking the COM registration. Use this procedure.

1. On the client PC, close all Internet Explorer windows.
2. Open Control Panel > Programs and Features (Windows 7) or Add or Remove Programs (Windows XP).
3. Click the Search box and type WinCC.
4. Right-click WinCC DataMonitor Client and select Uninstall. Confirm any prompts.
5. Reboot the client PC. This step is required to release the COM registrations.
6. Re-open Internet Explorer and navigate to http://<server-ip>/WebNavigator/WebClient.asp.
7. The server will detect that the WebNavigator client is not installed and will prompt to install or update it. Accept the prompt. The WebNavigator OCX is delivered via the signed ActiveX push from the WinCC web server.
8. After the OCX install completes, restart Internet Explorer and reconnect.

6.1 Registry Validation

After the reinstall, confirm the correct COM registration is in place:

reg query "HKLM\SOFTWARE\Siemens\WinCC\WebNavigator" /s
reg query "HKCR\CLSID\{B1E2D8C2-0000-0000-0000-000000000000}" 2>nul
dir "%LOCALAPPDATA%\Downloaded Installations\WinCCWebNavigatorClient.dll"

The exact CLSID will differ by WinCC version. The presence of WinCCWebNavigatorClient.dll in the Downloaded Installations folder and a populated HKLM\SOFTWARE\Siemens\WinCC\WebNavigator key confirms a clean install.

7. Solution 3 - Internet Explorer Reset and Clean Reinstall

Used when neither Solution 1 nor Solution 2 resolves the error, and as the only known fix when the client has been exposed to multiple WinCC server versions over time (for example, V7.0 SP1, V7.0 SP2, and V7.0 SP3 HF4 in the Recent Servers list).

1. Back up any IE favorites and offline content.
2. Open Control Panel > Programs and Features and uninstall Windows Internet Explorer 9.
3. Delete the following directories manually:
   • %LOCALAPPDATA%\Microsoft\Internet Explorer
   • %APPDATA%\Microsoft\Internet Explorer
   • C:\Users\<user>\AppData\Local\Microsoft\Windows\INetCache
   • %LOCALAPPDATA%\Downloaded Installations (this removes any cached WebNavigator or DataMonitor OCX)
4. Run cleanmgr /sageset:1 and select all temporary file categories. Execute cleanmgr /sagerun:1.
5. Open regedit as Administrator. Back up the registry. Then delete the following keys (reboot to safe mode if the keys are locked):
   • HKLM\SOFTWARE\Microsoft\Internet Explorer
   • HKCU\SOFTWARE\Microsoft\Internet Explorer
   • HKLM\SOFTWARE\Siemens\WinCC\WebNavigator
   • HKLM\SOFTWARE\Siemens\WinCC\DataMonitor
6. Reboot.
7. Reinstall Internet Explorer 9 from the official Microsoft distribution. Confirm the version under about:version.
8. Open Internet Explorer and navigate to http://<server-ip>/WebNavigator/WebClient.asp. Accept the ActiveX prompt to install the WebNavigator client.
9. Confirm the login dialog appears and the runtime picture loads.

This procedure has been confirmed in the field against WinCC V7.0 SP3 HF4 across a Juniper NetworkConnect 7.1.0 VPN tunnel. After the IE9 reinstall, the DataMonitor splash no longer appears and all picture tree, alarm, and trend controls operate normally.

8. Solution 4 - Operating System and Browser Compatibility Verification

Where multiple Windows client variants are deployed, isolate the failure to the OS layer before applying any of the above fixes.

The WebNavigator ActiveX runtime is a 32-bit COM component. On Windows 7 64-bit, Internet Explorer 10 and later default to 64-bit. Always launch the 32-bit IE explicitly:

"C:\Program Files (x86)\Internet Explorer\iexplore.exe"

9. Verification Procedure

After applying any of the four solutions, run the following verification sequence to confirm the client runtime is fully functional.

1. Open the 32-bit Internet Explorer (see path above) and navigate to http://<server-ip>/WebNavigator/WebClient.asp.
2. Confirm the login dialog appears within 5 seconds.
3. Log in with a WinCC user that has at least Operator rights.
4. Verify the start picture loads. Expect a 10-15 second load on the first connection, faster on subsequent logins.
5. Open the Picture Tree. Confirm at least one node expands and that clicking a child picture opens it.
6. Open the Alarm Window. Confirm the header shows Online (not Not active) and that pending alarms are visible.
7. Open a Trend/Online Trend Control. Confirm at least one archived tag is plotting.
8. Trigger a controlled process change and confirm the alarm and trend update in real time.
9. If reporting is required, open the Reports dialog. Confirm at least one report template is listed and that Print Preview returns data.
10. Close the browser, reopen it, and reconnect. Confirm a normal login without any DataMonitor splash.

10. Troubleshooting Matrix

Use this matrix to triage symptoms to solutions without re-running the full diagnostic.

11. Preventive Measures

Apply the following engineering practices on every WinCC WebNavigator deployment to prevent recurrence.

• Document the publication mode in the project README. Record the Web Configurator dropdown selection, the default ASP page served, and the date of the last republish.
• Standardize the client image. Build a Windows 7 32-bit golden image with Internet Explorer 9 (32-bit only) and only the WebNavigator Client OCX pre-installed. Never pre-install DataMonitor Client on WebNavigator-only terminals.
• Use dedicated client PCs per server type. When a single PC must connect to multiple WinCC servers, segregate the servers by publication mode and avoid mixing V7.0 SP3 with V7.0 SP1 / SP2 if at all possible.
• Disable IE9 automatic updates on terminal PCs to prevent the OCX registration from being invalidated by a stealth update.
• Add the WebNavigator URL to the Trusted Sites zone with the security level set to enable signed ActiveX controls.
• Test every WinCC service pack and hotfix in a lab before rolling to production; specifically test WebNavigator publication mode after each WinCC upgrade.
• Enable WinCC diagnostic logging. Set the registry value HKEY_LOCAL_MACHINE\SOFTWARE\Siemens\WinCC\WebNavigator\TraceLevel = 2 and tail %ProgramData%\Siemens\WinCC\WebNavigator\Logs when issues recur.
• Plan a migration path to WebUX for any new deployment. WebUX is HTML5-based and does not depend on the Internet Explorer ActiveX runtime, eliminating all four root causes described in this article.

12. Related Siemens Knowledge Base Entries

The following official Siemens industry support entries are directly relevant when troubleshooting WebNavigator publication mode and runtime behavior:

• WinCC Basic Options V7.5 SP2: WebNavigator, DataMonitor, WebUX - documents the ServiceMode runtime behavior and WebNavigator/DataMonitor coexistence rules.
• General Information about WebNavigator - documents the >20-second server-down detection delay on the client.
• FAQ: WinCC WebNavigator installation and configuration - covers the Web Configurator publication modes in detail.
• FAQ: WinCC WebNavigator client error messages - catalog of WebNavigator client-side error messages and resolution steps.
• FAQ: WinCC WebNavigator licensing - covers the licensing prerequisites for the WebNavigator and DataMonitor options.

Frequently Asked Questions