Player can't connect to server- freezes "Parsing Game info"

I set up a listen server for me and my friends who recently bought the game. For whatever reason, one of them can’t connect. He starts to, but it stops loading at “Parsing game info”. This seems like it would be an issue that comes up enough. He’s forwarded his ports for GMod and I don’t think it’s server-side, because the other player connects fine.

Example of the console for him trying to connect several times:

I get the same problem trying to join his server, but our other friend is capable of joining his server also.

So basically, 1 of us can join eithers’ game and we can’t join each other’s.

Does that mean all of you can connect to the 3rd friend? I was going to guess this was a firewall issue, but normally that would block all traffic and not just a specific IP. Can all 3 of you join a 3rd party dedicated server?

We all can join a dedicated server, and neither of us can connect to the third friend.

Same problem for me except it freezes at “retrieving server info” but it happens for every server.