I am able to load my Plex server and do an initial scan (both on mobile data and wifi on my home network). Shortly after, Symfonium shows the Plex server as offline on both mobile data and home network.
Apologies, it seems like that problem has resolved itself. It seemed to get better when I activated debug mode. I thought I had recreated the problem, but apparently not. The problem had been that it was never re-connecting to the Plex server. As you say, it is now.
Depending on you router and network the switch can take some times due to timeouts instead of rejections.
You can press the offline button in the filter page to sometime accelerate the process.