Following Plex’s recent data breach, I had changed my account password. After that my server wouldn’t show up in the players and clients anymore. Also
$plexhost:32400/web would show the Browser Interface but still no servers. Reconnecting the server to my account within the web app by logging in there didn’t work either.
Alternatively, a Claim Code can be requested under https://www.plex.tv/claim/, which ties a server to an account. This Claim Code then can be set as an environment variable for the Docker container and will be automatically picked up by the server.
After starting the container back up, the server should start to show up in your Account again.