(Plex remote access port mapped, but the port is unreachable from Plex.tv)

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. For more support you’ll need to share some more details from those checks.