exiled revenger Some one shared fix to it. https://forum.plutonium.pw/topic/31379/please-build-the-fast-file-associated-with-_____-dbsp-fix

@wheatlybananas if you installed off steam, make sure you have multiplayer installed as well to play some zombies maps. its a old fix on some maps

Click on install in Steam.
And yes you need to own the DLCs to download them on Steam.

Sounds like I'm okay, then.

NotZythe Thanks, i meant to edit my post a while ago. This fixed the issue.

VemX1Bot unfortunately plutonium doesn't pass out the game anymore so u wont get it here

Deegz12345 You must have the dlc installed!!!!