Remote access enabled, cannot access server over internet outside of LAN

No. That’s just the URL from where you’ll be opening the web app. The web app itself is running inside your browser and therefore accessing your media server locally (if you’re in the same network).

Did you already have a look at the related troubleshooting support article?

https://support.plex.tv/articles/200931138-troubleshooting-remote-access/

There’s also a guide with some more details on how to troubleshoot remote access issues (including some of the points raised by avg24).