It seems to be a common bug. Launch the game, hit f12. For some players it works, for others it doesn't. No more information on that, after f12 just nothing happens. There are 2 threads on Steam forum about it.
- Legacy ID
Launch the game. Press Steam screenshot key (f12 by default).
i dont want to sound mean but did you read my description? "For some players it works, for others it doesn't." You really think i didnt check that before i made this ticket? Even if it works for you, problem still exists for others. I'd say that by downvoting this you want others to not have that possibility to take screenshots like you do.