Cannot Join Multiplayer Games

Hello, I think this is more of a Steam problem, but I thought I’d ask here to see if anyone knew what my problem was.

So, whenever I try to join a game, I get this error message:
“This Steam account has been used to log in from another computer. To continue using Steam, you need to log in again.”

At the bottom of the box, there is a button that says, “Login,” so I click it, but when I do, it just brings me back to the Main Menu. I have the same problem in Counter Strike Source, but whenever I click “Login,” it actually brings me to a login box which will let me continue. I have tried restarting Steam and my computer, both did nothing. Any ideas?

Thanks!!

Ok, close Gmod.
In steam main window, go to ‘steam’ tab on the top, and click switch user.
Put your password in, and log back in.

Thanks, that solved the problem!