Update optional KB5012643, released for Windows 11 at the end of April, contains fixes for several bugs, but also causes some problems for users. In particular, this results in many applications not working properly after installation.

According to section Known Issues on the support page associated with the update KB5012643users who performed the installation have problems launching applications that use .NET Framework 3.5 components such as Windows Communication Foundation (WCF) and Windows Workflow (WWF). In this scenario, applications do not start correctly or stop working unexpectedly with errors.

For users experiencing the above issue, Microsoft recommends uninstalling the update by going to the Classic Control Panel and selecting the optional update KB5012643 from the list:

Reproduction / Fabio Roselin

If uninstalling the update is not an option for users experiencing the issue mentioned above, Microsoft recommends that you enable .NET Framework 3.5 from the Classic Control Panel using the option Turn Windows features on or off:

Reproduction / Fabio Roselin

Advanced users and IT professionals can do the same using the commands below from a command prompt run as administrator:

dism/online/enable-feature/featurename:netfx3/all
dism/online/enable-feature/featurename: WCF-HTTP-Activation
dism/online/enable-feature/featurename:WCF-NonHTTP-Activation

For users who have not yet installed the optional update KB5012643, Microsoft recommends that they wait until a final fix for the issue is available.

It’s worth remembering that this was not the only issue introduced in the optional KB5012643 update. A few days ago, this was confirmed to cause an issue in Safe Mode with no network connection on Windows 11 that causes the screen to flicker non-stop. Luckily, it was quickly and automatically fixed by the company using the Known Issue Rollback (KIR) feature – read more Here.

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Source: ExtremeTech