After changing any of these settings, I’d stop and restart the server.
Is your friend able to telnet IP 32400 using the problematic isp?
Using a custom domain can be tricky. Using “https://myhostname.com:32400” in Plex under “Custom server access URLs in Plex Network settings” you often end up with clients trying to use a Plex INC owned certificate which isn’t related to your domain so isn’t always “secure” . DNS doesn’t understand your port number. So really your Plex server is being found because Plex.tv is directing clients to your public IP:32400 using their certificate. If you disable Plex built in “Remote access” and use a reverse proxy you can direct all traffic over port 443 from your ‘https://myhostname.com’ into your home network and to local port 32400. Then with 'https://myhostname.com` in Plex under “Custom server access URLs in Plex Network settings” Plex.tv will simply direct your clients to ‘https://myhostname.com’ avoiding Plex INC certs. This is an alternative method if you can’t get the custom P12 certs to work in Plex server.
Thanks alot! The reverse proxy did it… I forwarded Plex‘ port to https://plex.myhostname.com:433.
My friend was able to access it without any problems.
