Read here: Banned from server
If you get the message "Banned from server. Try this:
When you have a dedicated server, inside the directory of the server, or in
C:\Users\ <username \AppData\LocalLow\IronGate\Valheim you have 3 files that is for the dedicated server.
Open the files named ‘adminlist.txt’, bannedlist.txt’,and permittedlist.txt’.
And add Steam IDs (one per line) to set desired roles. Check in these files and remove a user if needed.
(Example of a steam ID 76561198017260467 )
Please note that adding a person on the permitted list will ban everyone else from the