Maybe this is a STEAM question but I thought I would ask here first.

I have several games from the complete Mass Effect series, Skyrim, FO3, FO NV, Alien: Isolation as well as the complete Tomb Raider Package. F12 takes screenshots in ALL of those games BUT FO3. I have made sure since it was installed with steam that the overlay is checked. It is. I launch the game through Steam just to make sure. but nothing. Only the print screen button works.

Any ideas?

Not the end of the world but I'd like it working if possible.