"Host has downloadable content you do not."
Every time I try to join one of my friends’ games, I get the error message “You cannot join the match because the host has downloadable content you do not.” Is there a fix for this?
I would presume that you are on different game versions in conjunction to the new hot-fix. Have you downloaded it? if so, has he downloaded it?
Try restarting steam. Hotfix just went live a bit ago.