(Qnap) Plex web app not working but accessing directly off the server works

I have a weird one. If I log in to plex via my server via the 192.168.x.x address everything works fine, but if I run the web app (https://app.plex.tv/desktop/#!/server/ …) it is buggy and crashes all the time and most movies don’t play. This never was an issue but only became so some time recently.

My best guess is that I tightened up some access settings on my Qnap after their recent attacks and have probably removed a setting required for streaming over the web.

Does anyone have any idea what would cause this?

It sounds like you might have closed off the Remote Access port.