co-op campaign wont work

[Izanagi]

basically after the latest update me and my mate played left4dead two, before the update everything worked fine, after we played we selected the custom campaign we downloaded started to load it, then the loading bar dissapeared and wouldnt load the campaign.

tried reinstalling doesnt work
tried hosting a game, then it happens to my mate
i get invited to play happens to me
i got no conflicting addons
checked on internet im not the only one having this problem, but there is no mention of a solution.

[Kitsune]

Have you tried one of the standard campaigns? If they work just fine, then I imagine it has to do with not having the same exact versions of the campaign. I'm not sure how finicky the engine is with versions, however both of you should try downloading the same version from the same location at the same time.

[Izanagi]

when playing with a friend even the standard campaigns wont load, only single player, multiplayer without a friend seems to work

[Kitsune]

That's very odd, try opening a ticket with Support. If no one else has gotten an answer, your next best bet is to ask the providers of the game.

[Izanagi]

thanks for the advice might report the game problem to valve and see what they say