Can't join P2P Servers

I can’t join p2p servers, and friends can’t join me if I host a p2p server. It loads everything properly and eventually reaches ‘Lua Started!’ and then… nothing. Doesn’t freeze. Doesn’t lag. Doesn’t crash. Just nothing. Doesn’t matter how long I wait.

I’ve tried:

  • Reinstalling.
  • Factory reset.
  • Verifying integrity of game cache.
  • Joining with zero addons enabled for me and server host.
  • Joining with firewall completely disabled. GMOD is allowed through public and private networks.

I can join dedicated servers.

I’ve got no idea what to do now.