L4D2 CAMPAIGN GLITCH PLZ HELP

[Cumsley]

In singleplayer when i try to play campaigns other than Dead Center, no campaings show up. It only says Addon Campaigns, and those are the only other Campaigns I can play. I can't play any of the original campaigns and there is no online solution. PLEASE HELP!

[bob]

Verify files; remove recently installed workshop mods and re-verify

[Cumsley]

Thanks, I'll try.