No game session attached on this process on AcceptPlayer

the issue is simular to this

the cause might be
" * Or you are doing multi-process and you have multiples servers listening on the same port. 1 servers has the game session, but another server is receiving the player sessions. Check what you are reporting in ProcessReady for your servers, ensure your servers are listening on different ports (if using multi-process) and/or consider scaling down just to 1 server per instance to troubleshoot."

I can confirm that there are 50 process running in the instance as I have set it up in Concurrent processes in fleet dashboard.

But my question is, how can we run muiltiple process in one device that we can generate port dynamically?

Port allocation is typically handled on the actual program side, not by GameLift technically. For example, I belive Unreal Engine dedicated servers will automatically check if a port is already occupied by another Unreal server and will use another port if that’s the case.