I have a Plex server running on my PC -- latest version, no VPN activated. My other PC's, iPhone, iPad, wife's Android phone (Still on Kitkat) all see my server just fine over both my local network, and public internet.
I purchased two new tablets for my kids today (running Marshmallow), and installed the Plex app. Neither can discover my server via either local network or public internet. They can only see their own local content. I took one of their old tablets, and uninstalled/reinstalled Plex, and it can no longer see my server either!
I've tried the Plex client from both the Play store and Amazon, same scenario both ways.
Any ideas / thoughts?