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. The output of the individual steps can help if you need more support.
https://forums.plex.tv/t/the-basics-of-remote-access-troubleshooting/769517
