Invalid username or password

Hi, we have a strange problem regarding our new installation of gitlab-ee (16.3.2), all the clients on our network are able to log in with the username and password of the user defined, only on one machine the login does not work with the generic message “invalid username or password” but the same credentials on any other PC work without problems. We have already tried using different browsers clearing cache and cookies without success. What can we check on that PC to try to solve the problem ?

Ps. Under /var/log/gitlab wich is the log file that should cointain the login errors ?

keyboard? input language?
maybe type username / password in notepad first so you can see it’s correct, then copy / paste?
does logging in to other site work from that PC? like gmail or youtube or some other sites not related to gitlab?

Problem solved, there was a static dns to an older istance still online.