Direct answer
Velocity documents this exact message as an improper player-forwarding configuration. Make the proxy and backend use the same forwarding method and settings; for Paper modern forwarding, the backend secret and online-mode values must match Velocity.
What it means
Align Velocity and backend forwarding settings when the proxy cannot complete player information forwarding.
If you are a player
- Copy the exact connection/kick message and note the timestamp; similar-looking login errors can have different causes.
- Check the address, port, Minecraft version, and whether other players can connect at the same time.
- Tell the owner whether the problem follows your account/device/network or affects everyone.
If you run the server
- Choose one forwarding mode and configure the proxy and backend for the same mode.
- For Paper modern forwarding, set Velocity
player-info-forwarding-mode = "modern". - On the Paper backend, set
online-mode=falseinserver.properties, disable legacy Bungee forwarding, enableproxies.velocity.enabled, match the forwarding secret, and makeproxies.velocity.online-modematch Velocity. - Restart both sides and connect through Velocity, not the backend address.
References
Use the documentation for the exact software and release you run. These sources support the settings or diagnostic behavior used in this fix.
Focused diagnostic check: Check that the backend is configured for Velocity modern forwarding, that the proxy is using the same forwarding secret and that the backend is reached only through the proxy. Modern forwarding still requires backend network protection; opening an offline-mode backend publicly to “fix” login errors creates an impersonation risk.
- PaperMC: Velocity FAQ
- PaperMC: Velocity player information forwarding
- PaperMC: Velocity server compatibility
Related fixes and guides
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