Password quits working

PC Dell M4800 Laptop

OS 20.04

Re-installed OS three times

When I install the OS it completes successfully. Can log in with no difficulty. However after running ‘sudo apt upgrade’
I can not log back into the system. I enter the password at the user prompt and the system promptly displays my user
id again. I click on it and it prompts me for the password again. However if I enter a password that is not the right
password the system seems to go into a delay routine, then displays the message, “Sorry, that didn’t work, please try
again”. Um, which way do I go?