when i join a server, ill just get an error saying that im logged on at another computer

allways when i join a server an error pops up saying that i must reconnect to steam.
can someone please come up with an answer to my problem?
-and dont just say “reconnect to steam…”
Ive reconnected to steam several times and even changed my password, so what can the problem be?
please answer.

Change your password.

Ignore above.
Log out, log back in.
If that fails, log out, go to your steam folder and delete steam_registery.blob and log back in.