I had the exact same issue. It is an issue with the current Android app version. Here is a work around:
- Uninstall Plex from your Android
- Go to Plex for Android - #502 by PlexAndroidReleaser on your Android
- Scroll to almost the bottom, and download “Plex for Android 10.26.0” to get the previous version of the app.
- Install
- ???
- Profit
Idk what Plex broke in the current app, but it doesn’t work for remote access for a lot of people now. I’ve read it has to do with CGNAT which sucks because I don’t want to have to pay my ISP to remove me from it.