If that doesn’t work for you, I had to fix some other things, to get mine working for the first time earlier this week, as described here: Plexamp for Raspberry Pi - How to create a new server.json file now older desktop versions of Plexamp no longer work - #6 by IvanKaramazov . Even before that I had to manually add the server info to my server.json, since the old desktop apps also can’t connect to the media provider list anymore.
