Hi there and welcome
Can you on the sign in screen, hold down SHIFT and with it held down, click on the power icon and click on restart.
Still with shift held down, let it restart until you are at a menu.
Choose from the menu, Troubleshoot, then advance then choose System Restore.
Follow the onscreen steps and perform a system restore choosing the last restore point in the list.
Let this complete and tell me if you can then sign in please.,
Thanks, ***** ***** know the results please.
How did it go?