Need more info
We're aware of the issue and we're working to come up with a fix. Unfortunately right now we haven't been able to reproduce the error locally, so that slows us down considerably. I'd like to get some info from everyone experiencing the problem to try and reduce it down to the most simple case.
Please send me a private message with more information to keep the thread at a minimum.
Has anyone experienced this problem while trying to play a map from their co-op queue? In other words, you've subscribed to a co-op map on the Workshop and your co-op partner has subscribed to the same map, then you start a co-op session and are disconnected from Steam.
Or, does this only occur for you when playing quickplay co-op maps?
Again, please send me a private message and we'll see if we can't get more clarity. Thanks for your patience and help as we try to get to the bottom of the problem.