Howdy KenPeteGa,
It sounds like you have an update that will not install because it keeps giving you the error that it cannot be verified. I would boot to safe mode to help alleviate this issue. It will perform a disk verification and repair if necessary as well as clearing out some system level caches which I feel should help you out:
Follow these steps to start up into safe mode.
- Start or restart your Mac.
- Immediately after you hear the startup sound, press and hold the Shift key.
- Release the Shift key when you see the Apple logo appear on the screen.
After the Apple logo appears, it might take longer than usual to reach the login screen or your desktop. This is because your Mac performs a directory check of your startup disk as part of safe mode.
To leave safe mode, restart your computer without pressing any keys during startup.
From: Try safe mode if your Mac doesn‘t finish starting up
When you log into your user in safe mode, restart as normal and test the issue again. Thank you for using Apple Support Communities!
