A machine is already yours

What the screen says

A session holds a whole machine, so one account holds one at a time.

3 things to try

1. Select Play here instead. Walter ends the other session and starts this one on the screen you are on.
2. The other screen loses the game within a moment, as if Exit was pressed there. Progress the game saved to Steam is kept.
1. Think where you last played. A laptop lid closed on a live session keeps it live.
2. Open that device and select Exit at the top of the play screen.
3. Come back here and press play again.
1. Leave it for an hour. A session with nothing happening in it ends by itself.
2. If you need it sooner, select No, tell us and say roughly when you last played.

Worth knowing Two people cannot play on one Walter account at the same time. If you share yours, this is what that looks like.

Did this fix it?