@Andre-Zucco Deleting an account is unnecessary.
All info points to an issue between your signature file and the device.
In particular the signature file is detecting a mismatch between the device name and what is on the signature file.
This happens when someone migrates files from an older device or changes the device name.
Deleting the signature file at C:\Users\SomeName\AppData\Local\SCF Licenses and restarting SketchUp should fix your signature issues.
But from your replies this has not rectified it. This suggests there is something else that is causing instability.
Hopefully @TIG @Gabor or even @fredo6 might have further options.