Cannot start the appocolipse

[legendbadger]

hi guys,
i bought GTA from Steam 3 days ago and wanted to play the zombies on it.
I believe i have downloaded all the stuff to play but when i press F4 it comes up with "warning saying unable to resolve api version 2.9.4"
being new to laptop gaming I havnt tried anything yes except restarting the game.

thanks in advance