Control channel never registers after successful claim — isolated to backend/version issue, not a client-side build problem

Hi everyone,

Following up on an issue I’ve been debugging for a while. Running Purpur 1.21.11 with the Minecraft companion plugin.

Short version: claim succeeds (agent shows correctly in my dashboard), but the control channel never registers, and the dashboard permanently shows “Agent is offline” / “Not connected”. This happens every single run:
[PlayitPlugin] Failed to register control channel: gg.playit.proto.rest.ErrorResponse@17bf59ef

What I’ve done to rule out client-side causes:

  • Confirmed hosting doesn’t block outbound traffic

  • Confirmed playit.gg itself isn’t down

  • The official 0.1.1-paper build doesn’t even start on 1.21.11 (NoSuchMethodError: DedicatedServer.isEpollEnabled() — looks like this method was removed server-side in newer MC versions)

  • Rebuilt from the pristine official 0.1.1 source with exactly one minimal, non-network-related fix (just removed the now-nonexistent isEpollEnabled() call so the plugin can actually start) — no changes to claim/agent/networking code

  • With that minimal build: plugin loads fine, claim succeeds, but control channel registration still fails with the same error every time

    Since the only change made was unrelated to networking/protocol code, this doesn’t look like a build issue on my end anymore. I only have access to the Minecraft server process itself (no SSH/shell), so I can’t test with the standalone playit-agent instead.

    Has anyone seen this recently, or is there a known issue with the client version fingerprint used during registration (looks like it’s been hardcoded to the same value since the 0.1.0 release)? Any pointers appreciated!

The Playit Minecraft plugin release “0.1.1”? We’re now on “0.2.0” old versions will not work. Releases · playit-cloud/playit-minecraft-plugin · GitHub