Core Keeper players cannot join with the Game ID

Core Keeper connection problems nearly always come back to the Game ID. Work through this list in order.

1. Check the Game ID in the console

1. Open the Console tab in the Game Panel.
2. Restart the server and read the Game ID it prints as it loads.
3. Compare it character for character with what your players are using.

If they differ, the config was regenerated at some point. Set a fixed gameId in ServerConfig.json so this cannot happen again.

2. Check the ID is valid

• At least 28 characters.
• No zeros.
• No punctuation, letters and numbers only.

An invalid ID is quietly replaced with a generated one, which is why your players end up with the wrong code.

3. Check the server is actually up

• The Game ID only works while the server is running. A stopped server looks identical to a wrong ID from the player's side.
• Watch the console during a join attempt. A connection that reaches the server is logged.

4. Version mismatch

Steam updates your players' clients automatically. Restart the server from the panel so it takes the same update, and wait for the console to settle before trying again.

5. Server full or world not loaded

• Check maxNumberPlayers in ServerConfig.json.
• A large world takes a while to load on start. Wait for the console to report the world is ready.

6. The config will not load

ServerConfig.json must stay valid JSON. A trailing comma or a missing quotation mark makes the server fall back to defaults, which includes generating a new Game ID and possibly a new world. If your world and ID both changed at once, this is why. Restore the file, fix the JSON and restart.

Open a ticket from Support in the Client Area with the console output and the Game ID you expect if none of this fits.