Ok yup we tried to test with someone outside our organization tonight and ran into the same thing! Switched the backend over to Steam with the 480 appID but still running into issues. Off the top of your head was there anything else you needed to do to get it to work? We keep running into something like this when attempting to FindSession:
[2023.09.26-05.27.37:243][153]LogOnlineSession: Warning: STEAM: Server response IP:[random IP 1] [2023.09.26-05.27.37:244][154]LogOnlineSession: Warning: STEAM: Removed incompatible build: ServerBuildUniqueId = 0x00000000, GetBuildUniqueId() = 0x019a995c [2023.09.26-05.27.37:245][154]LogOnlineSession: Warning: STEAM: Server response IP:[random IP 2] [2023.09.26-05.27.37:245][154]LogOnlineSession: Warning: STEAM: Removed incompatible build: ServerBuildUniqueId = 0x00000000, GetBuildUniqueId() = 0x019a995c [2023.09.26-05.27.38:831][607]LogOnlineSession: Warning: STEAM: Failed to respond IP:[My - host - IP] [2023.09.26-05.27.38:871][619]LogOnlineSession: Warning: STEAM: Failed to respond IP:[random IP 3] [2023.09.26-05.27.38:873][619]LogTemp: Warning: Found 0 sessions!