Friend Can't Join Co-op Server

[SpazzMan502]

Hello, 

My friend and I have played Project Zomboid for quite some time, and we've progressed far into our game. I host the server through steam and invite him through the invite menu, and this has worked out for a few weeks up until recently. For some reason, when he tried joining the server, he got a black screen saying "Connection to server lost" and he has no way of connecting. He's tried reinstalling the game multiple times on multiple drives, deleting his Zomboid folder and reinstalling, checking steam files, and everything we could think of.

I've validated my steam files and re-checked the ports that were supposed to be forwarded.
 

We're running on the current stable build (38.30)

The server is using Bedford Falls as its only mod, and he's been able to connect with it previously

 

We've been trying to solve this for a couple of days, so any help would be greatly appreciated.


Thank you!

[FinestHops]

The first thing I would look at is your windows firewall. Maybe an update changed something or one of a million other causes for it to act up. As a test only, I would turn off the windows firewall and try again. If they connect, you know its your firewall. If they don't, more testing of other potential causes is needed. Firewall off the bat seems like the most likely culprit though.