The certificate expired on 31 October and Microsoft warns that some Windows 11 users aren't able to open apps like the Snipping Tool, touch keyboard, or emoji panel.
Vole has come up with a patch KB4006746 and is available to fix some of the bugs, but it's currently in preview, meaning you have to install it manually from Windows Update.
However the patch, KB4006746, will fix the touch keyboard, voice typing, emoji panel, and issues with the getting started and tips sections of Windows 11.
It can be found in the updates in the Windows Update section of Settings in Windows 11. However it does not fix the Snipping Tool app.
"To mitigate the issue with Snipping Tool, use the Print Screen key on your keyboard and paste the screenshot into your document. You can also paste it into Paint to select and copy the section you want."
This is the latest in a number of embarrassing moments that Microsoft has had with Windows 11, which does not run on many older hardware chips and lacks much in the way of compelling apps over Windows 10 which works rather well.