Hello,
I’ve been trying, unsuccessfully, to get Remote Access to work in China. I have turned off all my VPN settings and even my firewall on my NAS and I have had no luck. I’ve gone through my tomato router settings and I’m confident they are correct so my last option is to check if it works in China.
Is your Plex server outside of China? If so it’s probably blocked by the great firewall the China uses. This of course is just a guess but China restricts many things so I would not be surprised.
You are going to have to use VPN to access Plex. There are a few good ones out there, while you need to avoid some of the mainstream ones like Hide My Ass which blocked by China.