Most problems with a Core Keeper server come down to a few causes. Start with the one that matches what you see.
Friends could join yesterday, but the code is rejected after a restart
Why: The Game ID setting is empty, so the server can create a different Game ID when it starts.
Fix: Set your own Game ID in the settings (15 to 28 letters and numbers, no Y, y, x, 0 or O) and restart. Share that code once and it stays the same.
I typed the address and port from the Overview page and cannot connect
Why: Core Keeper players join with a Game ID, not an address.
Fix: Use Join Game on the main menu and enter the Game ID from GameID.txt in Files, or the one you set in Settings, then Game Settings.
The server ignored the Game ID I set and made a different one
Why: The code is the wrong length or contains a character the game does not accept.
Fix: Use 15 to 28 letters and numbers only, without Y, y, x, 0 or O, then restart.
A friend on another platform cannot join with the Game ID
Fix: The Game ID is the way to join your server. Check it matches exactly, then ask support and tell us the friend's platform and the exact message they see.
I changed the World Seed or Hard mode but my existing world did not change
Why: Those settings are only read when a world is first created.
Fix: Set World Index to an unused slot so a new world is built with the new values. Your old world stays on disk.
The server seems stuck after the first start, or after switching to a new world slot
Why: Generating a new world takes a while, about five minutes.
Fix: Wait for the Console tab to settle before joining or restarting. Restarting in the middle only starts the wait again.
I typed an admin command in the Console box and nothing happened
Why: The Console tab on the server page does not send input to Core Keeper, and the game has no remote admin tool.
Fix: Manage admins and bans from the pause menu in game, or edit Admins.json in Files and restart the server.
I added myself to Admins.json but I am still not an admin
Why: The file is only read at start, or the entry uses a Steam name instead of the Steam64 ID.
Fix: Check that the entry has your Steam64 ID (the long number), save the file, then restart the server.
Still stuck?
Open a ticket in the category that fits and include the last 50 to 100 lines of the console. See How to open a support ticket and How to fix a server that will not start.
