losing emails after upgrade

I am using version 20.04 and recently received an update to Thunderbird which I authorized and got confirmation my computer was up to date.Since then my emails show for about 2 min and then disappear.They are not in trash,archives,or junk,just gone.This means I've lost an unknown number of emails which disappeared before I could even read them.I can send which goes to sent.I checked account settings and confirmed that it is set to IMAP and even asked it to repair folder but nothing happens.There is no box to check"leave messages on server " or "until I delete". Please respond to my alternate address <email address hidden> so I can see your response.