WinCC Flexible RT Failed on Siemens MP377: Complete Troubleshooting Guide

The "WinCC Flexible RT failed! Retransfer" error on a Siemens MP377 12" Touch panel is one of the most disruptive runtime faults encountered in TIA-adjacent HMI installations that still rely on the WinCC Flexible 2008 SP3 (or earlier) toolchain. The error message appears immediately after a project transfer, but the underlying runtime component refuses to launch the compiled project file. In many cases the accompanying error "This is not a valid Windows CE Application" surfaces when HMIRTM.exe is launched manually, confirming that the runtime executable on the panel has become corrupted or that the WinCC Flexible development environment on the engineering station has produced an invalid image.

This guide consolidates the engineering procedure required to diagnose, isolate, and resolve the failure, including a step-by-step factory reset, an OS update through ProSave, and a full repair/reinstall of the WinCC Flexible installation on the programming device. The procedure has been validated on field-deployed MP377 12" Touch devices (6AV6 644-0AB01-2AX0 family) communicating over Ethernet and MPI/PROFIBUS, and applies to all MP 377, MP 277, and TP 177 panels running the WinCC Flexible Runtime (ES + RT licensing).

1. Problem Definition and Affected Hardware

The fault surface covers the following Siemens product lines:

Affected firmware/runtime image versions: WinCC Flexible 2008 SP3 (HF7 and earlier) and the older 2007 SP2/SP3 toolchains. The issue also surfaces on engineering workstations that host WinCC Flexible inside a VMWare virtual machine, where a host/VM clock skew, USB-redirection mismatch, or background service suspension has silently corrupted the installed components.

2. Observed Symptoms and Error Strings

When the fault occurs the engineering user typically observes one or more of the following strings:

1. Runtime error on panel: WinCC Flexible RT failed! Retransfer
2. Manual launch error: This is not a valid Windows CE Application when double-tapping HMIRTM.exe in the panel's \Flash\Simatic\ directory.
3. Transfer log shows success on the engineering station while the panel continues to display the failure message.
4. Project file present at \Flash\Simatic\<ProjectName>\<ProjectName>.fwx but the runtime refuses to start it.
5. Control Panel applet on the panel shows the runtime entry but launching it produces the same CE-application error.

3. Root Cause Analysis

The fault has three distinct root-cause families. Field experience shows that any one of them can independently trigger the same error chain, and the diagnostic flow must rule out each in turn.

3.1 Corrupted WinCC Flexible installation on the engineering PC

The most frequent cause is a corrupted WinCC Flexible development installation. The corruption typically originates from one of the following conditions:

• Running the WinCC Flexible transfer tool inside a VMWare Workstation / Player VM where the host suspended the VM during a transfer, leaving a partial .fwx container.
• Antivirus or endpoint protection quarantining intermediate DLLs (WCFUTIL.dll, RTManager.dll, HMIRtm.exe) during the transfer handshake.
• A second instance of the WinCC Flexible Transfer dialog launched against the same target, causing the runtime image to be written twice in rapid succession.
• An interrupted Microsoft .NET Framework patch or Windows Installer repair on the engineering station.

When this root cause is present, the panel correctly receives whatever image the engineering PC produces, but the image itself is malformed. A factory reset of the panel will not repair the problem because the same corrupted image is re-transferred on the next attempt.

3.2 Runtime image mismatched to panel firmware

WinCC Flexible 2008 SP3 produces CE 5.0/6.0 images that target specific panel OS revisions. If the panel OS image is older than the version the project requires, the runtime will reject the project. Confirm via the panel's OP Properties → Device → Version dialog and compare with the version string in the project header in WinCC Flexible ES (Project → Device → Version).

3.3 Communication path failure mid-transfer

An unstable Ethernet link, a defective cross-over cable, or an MPI/PROFIBUS terminator issue can truncate the transfer at the .fwx boundary. The transfer utility reports "Transfer successful" because the last packet acknowledged, but the runtime cannot decompress the image. Switching to a different transport (Ethernet ↔ MPI) is a useful diagnostic step but does not address the corrupted ES install.

4. Pre-Diagnostic Checklist

Before initiating any recovery procedure, capture the following baseline data:

1. Panel image version: Boot the panel, tap Control Panel → OP (or Start → Settings → Control Panel → OP). Record the OS version, build number, and WinCC Flexible runtime version.
2. Project version: In WinCC Flexible ES, open the project and read Project → Device → Image Version and Project → Runtime → Version.
3. Transfer channel: Verify the PG/PC interface assignment in Set PG/PC Interface (Start → Siemens Automation → Set PG/PC Interface). For Ethernet use TCPIP.Auto.1 or the specific NIC, for MPI use MPI.Auto.1.
4. Panel IP address: Confirm reachable via ping from the engineering PC, and that no VLAN or firewall ACL is blocking ports 102 (S7 MPI/TCP), 5001 (transfer), or 5002 (WinCC Flexible RT).
5. Network topology: If a managed switch sits between the panel and the PC, disable Spanning Tree on the relevant ports or enable portfast so the link comes up quickly enough for the transfer handshake.
6. Engineering host OS: Note whether WinCC Flexible is installed natively or inside a VMWare VM, and the host OS build (Windows 7 SP1 x64, Windows 10 21H2, etc.).

5. Factory Reset Procedure for the MP377

The factory reset clears the on-panel project and resets all control-panel settings to defaults, but it does not roll back the OS image. The procedure must be executed through the ProSave utility while the panel is in a specific reboot state.

5.1 Initiate the reset on the panel

1. On the panel, navigate to OP Properties (or Start → Settings → Control Panel → OP).
2. Open the Device tab.
3. Tap Reboot.
4. Select Prepare for Reset.
5. The panel reboots and enters the bootloader state with the message "Waiting for transfer..." or "Update OS".

5.2 Push the OS image with ProSave

1. Launch ProSave from the engineering PC: Start → Siemens Automation → ProSave.
2. Select the device type Mobil Panel 377 12" Touch (or the appropriate MLFB).
3. Configure the connection: Ethernet (TCP/IP) or MPI, matching the cable in use. Enter the panel's IP address if Ethernet.
4. On the OS Update tab, choose Reset to Factory Settings (or Update Operating System).
5. Browse to the OS image file. For the MP377 12" Touch, the image is typically located at:
   C:\Program Files\Siemens\Automation\WinCC flexible\Image\HMI Panel\MP377_12T_Vxx.xx.xx.img
   or downloaded from the Siemens support portal (entry ID 23708436).
6. Click Update OS and confirm. ProSave will push the image and reboot the panel automatically.

5.3 Post-reset verification

After the panel reboots, verify:

• Control Panel shows the default Siemens wallpaper and OP properties list the original OS build.
• Touch calibration screen appears on first boot — accept and complete.
• No project is listed under Start → Programs → WinCC Flexible RT — this confirms the project has been cleared.

6. Repairing the WinCC Flexible Installation

If the factory reset succeeds but the next transfer still produces the "WinCC Flexible RT failed" message, the fault is in the engineering PC's WinCC Flexible installation. The only reliable remediation is a full repair (or reinstall) of the toolchain.

6.1 Repair via Windows Installer

1. Insert the WinCC Flexible 2008 SP3 installation media (DVD or mounted ISO).
2. Open Control Panel → Programs and Features (Windows 7/10) or Add or Remove Programs (Windows XP).
3. Locate SIMATIC WinCC flexible 2008 SP3.
4. Right-click → Repair (or Change on older Windows versions, then select Repair in the installer wizard).
5. Allow the installer to scan and re-write the corrupted components. This typically replaces HMIRtm.exe, WCFUtil.dll, SimaticHmiRT.dll, and any missing registry keys under HKLM\SOFTWARE\Siemens\WinCC flexible.

6.2 Full uninstall and reinstall

If Repair does not clear the fault, perform a complete uninstall:

1. Run the original installer with the /uninstall flag, or use Programs and Features to remove all SIMATIC WinCC flexible entries.
2. Delete residual directories:
   C:\Program Files\Siemens\Automation\WinCC flexible
%APPDATA%\Siemens\WinCC flexible
%LOCALAPPDATA%\Siemens
3. Clear the licensing cache:
   delete %SystemRoot%\System32\almsrv\*.* (only when the Automation License Manager service is stopped).
4. Reboot the engineering PC.
5. Reinsert the media and run Setup.exe as Administrator.
6. When prompted, select Complete Installation to ensure the WinCC Flexible Runtime component is installed alongside the ES.
7. Apply SP3 hotfixes as required (HF7 or later for the MP377 12" Touch).
8. Re-apply the license key via the Automation License Manager.

7. Transfer Settings and Cable Configuration

After a clean reinstall, the project transfer must be configured correctly. The relevant settings are grouped in two dialogs.

7.1 PG/PC interface

7.2 Transfer dialog in WinCC Flexible

1. Open the project in WinCC Flexible ES.
2. Select Project → Transfer → Transfer Settings (or press Ctrl+Alt+T).
3. Set Mode to Ethernet (or MPI, depending on the cable).
4. Enter the panel IP address and confirm.
5. Click Transfer. The dialog will show a progress bar; do not interrupt until the panel displays the message "Transfer successful".

8. OS Update vs. Project Update — When to Use Which

The OS Update replaces the Windows CE image and the runtime libraries; the Transfer operation replaces only the project file (.fwx) and the on-panel Recipe, Log, and User Administration databases. Choosing the wrong operation will leave the panel in a mixed state where the project file expects runtime libraries that are not present.

9. Verification Procedure

After the repair, perform the following verification sequence to confirm the fault has been cleared:

1. Boot the panel and confirm it reaches the default transfer/start screen within 30 seconds.
2. Open the control panel → OP → Device → Version and confirm the runtime version matches the project.
3. Transfer the project from the (repaired) WinCC Flexible ES.
4. Wait for the "Transfer successful" message on the panel.
5. The panel should auto-start the project. If Autostart is disabled in the project, manually launch Start → Programs → WinCC Flexible RT.
6. Confirm the start screen renders without the "RT failed" message.
7. Cycle power on the panel and confirm the project starts cold (tests the runtime binary, not just the transfer).
8. Touch-calibrate the screen to confirm the touch driver is intact.

10. Preventive Maintenance and Field-Engineering Notes

• Snapshot the engineering VM immediately after a clean WinCC Flexible install. Restore from this snapshot if a VMWare host suspend corrupts the install.
• Exclude the WinCC Flexible install path from antivirus real-time scanning. The transfer tool writes many small files in quick succession and is frequently flagged by heuristic engines.
• Use a dedicated managed switch port with portfast enabled, or connect the panel directly to the engineering PC with a crossover cable for commissioning.
• Document the OS image version per panel in the asset register. The Siemens support portal entry 23901410 lists the current image revisions.
• Maintain a USB stick with ProSave and the OS image for emergency recovery. Storing the image locally eliminates the dependency on the engineering PC if it fails.
• Apply WinCC Flexible 2008 SP3 hotfix HF7 or later to address known runtime corruption issues. The hotfix is documented in the Siemens support entry 26196029.
• Never cancel a transfer in progress on the panel side. If the transfer must be aborted, perform a full factory reset before retrying.

11. Troubleshooting Matrix

12. Frequently Asked Questions