If players see Sonar and then fail to enter the lobby, establish which phase fails. Make one attempt with a test account and compare the timestamp in the Velocity and lobby logs.
Separate verification from backend connection
If the player remains in verification, inspect Sonar’s log and the client version. If the proxy attempts the lobby connection, check the configured lobby host and port and the error Paper received.
player-info-forwarding-mode = "modern"
forwarding-secret-file = "forwarding.secret"
On a modern forwarding setup, use the corresponding Velocity settings below. Enable Velocity support in Paper’s config/paper-global.yml and check that its secret matches the proxy file. Paper’s Velocity online-mode should match the proxy’s online-mode.
Keep the secret out of logs and forum posts. After correcting the failing layer, test a regular join and a backend switch. Keep backend access limited to the proxy network.