I’ve been using Plex successfully for years now but every so often the Remote Access becomes unavailable outside my area. Sometimes a version update and a reboot works or switching the disable/enable tab. It may even clear itself, but today nothing seems to work. The only change is that I’ve subscribed to a VPN (NordVPN) so I’ve tried switching that off but it makes no difference.
I attach a screen shot which may indicate something
Unless your VPN provider can get you a static IP and you can port forward on the VPN that will probably not work.
Did you setup a port forward for your Plex?