You are logged in on another computer playing "<game>"

[Stavy]

My friend has two computers and yesterday I was at his house and we were playing stuff and I was logged into my steam on his 2nd PC. Today I went to play a game on my PC at home and when I click play on a game it says

"You are already logged into another computer playing "<Mount and Blade: Warband>" Launching "<game>" here will disconnect the other session from steam."

He is playing the game on the same computer I was playing on yesterday but he has logged me out of my account and is playing on his own. And even when I click on "Continue Launch" to play the game and sign him out the game starts preparing to launch but never actually does. And I don't know why it is doing this.
If anyone knows how to fix I will be very grateful.
Thank you

[ReBoot]

For starters, change your password and reauthorize all computers that aren't your current one from Steam guard.

[Stavy]

Actually Never mind I managed to fix it

[Stavy]

But thanks for help anyway :)

[Sebek]

How did you fix it?

[Stavy]

I just restarted my PC and it worked fine lol