Can't hit T to "invite friend"

[Kaboo]

When I'm on the mission screen, nothing happens when I press T on my keyboard.

[OzymandiasUnlimit]

Same issue here. I usually play with controller and that doesn't register anything either when pressings the prompted button to invite a friend.

[ArrowedKnee]

And why is it sometimes X to invite a friend and then T??
Neither key did anything.

[tenninjas]

This is still an issue now. It's beyond infuriating that I cannot play with my friend.

[J3FF-4-R4M4]

FIX... Make sure steam overlay is turned on.

[ArrowedKnee]

I did manage to play with my friend. The popup only showed up, when a friend actually had the game or demo installed.