Usually if you had plex server running and you’re switching deployment version, e.g. from truecharts to ix app or docker in a jail etc, you have to generate a plex claim token to claim your existing server, if you’ve not generated a plex claim token and specified it during the installation you can’t access your existing plex server. to generate a claim token you have to go to Claim | Plex
Edit: the plex claim token has a lifetime of 5 Minutes, so generate it if you’ve already setup the rest of the installation, otherwise it can be expired when you finish the setup.