Go to "https://account.plex.tv/claim" to get your claim code and run 'PLEX_MEDIA_SERVER_APPLICATION_SUPPORT_DIR="/config/Library/Application Support/" bash plex-claim-server.sh ${claim code}'
Verify the change 'cat "/config/Library/Application Support/Plex Media Server/Preferences.xml"'
Restart the container
Repeat the procedure several time if the server still cannot be claimed