A new Satisfactory server does nothing until someone claims it. That's done from inside the game, not the panel, which is why it catches people out.
- Start the server from the Console tab in the panel and wait for it to finish starting.
- Note the address and port. They're on the Network tab.
- In Satisfactory, open Server Manager from the main menu and click Add Server.
- Enter the address as
ip:port. - The game asks you to set an administrator password. It's set here, not in the panel, so pick one and keep it.
- Name the server, then start a new game or upload a save.