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

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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!