That’s really strange that it doesn’t work seeing as you can get https://79-11x.xx.xx.xxxxxx.plex.direct to resolve to the correct IP when doing a DNS check remotely. It should at the minimum connect to your Plex server and then throw up a certificate error when connecting via https://79-11x.xx.xx.xxxxxx.plex.direct.
Does just unsecured http://79-11x.xx.xx.xxxxxx.plex.direct work?
What is in your server logs? Are you seeing any connection attempts at all?
You could try requesting a certificate reset.
