Remote access troubleshooting can be tricky because you only control some of the puzzle pieces.
Sometimes, using the automatic forwarding can be the culprit, causing the connection to be disabled without further warning. In such a case it’s beneficial to use a manual port forward in your router configuration instead.
Remote access not working after a certain time could also mean you haven’t assigned a static local IP address to your Plex Media Server (IP reservation) – in which case your device gets a new local IP address every now-and-then and in consequence looses its remote connection (until you click retry).
The message you posted contains the link to the Plex Remote Access troubleshooting support article.
There’s also a guide in the forum on how to further investigate what’s causing your issue/hiccups.
