This is the stuff of DBA nightmares !
Q. Can you reset the SA account on server XXXXX, we think it has expired and now no-one can work.
Connect to Server:
Surely no-one would set up a Server with an sa account which expires?
Find sa password and change connection to use SA account.
Connect without issue.
Me. Have checked Server and account is fine.
A. Thanks that's great, you've fixed it we can all work now.