Plex local web app can't find the server
In the last few weeks no Plex client app has been able to connect to the Plex server on my Synology NAS DS412+, including a local web client. I have uninstalled the Plex server and reinstalled it, using both automatic and manual installation, but with no change. I have also tried the instructions at https://support.plex.tv/hc/en-us/articles/204604227-Why-can-t-the-Plex-app-find-or-connect-to-my-Plex-Media-Server-
Note, the Plex server is visible as a Device, but the client web app can't connect.