I was trying to play vanilla multiplayer with my friend and he is unable to join my game. However, he can join my multiplayer room, but on his side, no one is in the room. He tried just click "Ready" and let us start the game, but the game was just stuck until he actively quit the room, and the game suddenly loads. We tried sending each other messages in the room chat, but he is unable to receive any messages (or even see his own history message) but can send messages to me. Note that all the messages he sent appear to be sent by "System" on my side.
Some screenshots for more info:
My side:
His side:
We have tried everything we found online including completely reinstalling the game, disabling Windows Defender Firewall, turning on/off VPN, and even using a mobile hotspot... But none seems to work.
Does anyone know what the issue is here and maybe how to solve this issue?
Some screenshots for more info:
My side:

His side:

We have tried everything we found online including completely reinstalling the game, disabling Windows Defender Firewall, turning on/off VPN, and even using a mobile hotspot... But none seems to work.
Does anyone know what the issue is here and maybe how to solve this issue?