All right, so I changed my old modem for a new one and now that message above shows on my PLEX and my media looks awful. In my old modem, I’ve never had any type of problems, I just downloaded Plex and that was it. This is the thing that now appears on my TV:
Hi, I have the same problem. It is happening when streaming at home. I have my plex media server on a new (since Dec 24) synology NAS (DS224+) wired via Ethernet into one my Wi-fi nodes. My Amazon fire stick is in the same room as the node and I received the error above halfway through a movie when streaming on the fire stick. The streaming quality then significantly dropped. I switched to watch it via my Mac mini and the quality was similar (Mac mini also in the same room as the node).
This helped me get mine running. I felt so stupid when I realized I forgot to set up a firewall rule to match my port forward. I also had to go to the server console and check the box for it to use the specified port for the external port I opened. Once I did these it works great now without relay enabled. If your port is not showing open then that the problem. If not its probably the server side settings.