I finally have the Plex app working on the PS5.
I have a more complicated home network setup than most Plex users, including running my own DNS server and serving Plex via a HTTPS reverse proxy (including a lets-encrypt certificate). Here’s some of my findings on how I’ve come to believe how the Plex app works in the hope it helps you troubleshoot.
Upon starting the Plex app, if settings -> remote access is enabled on the server, the app will try and hit https://somerubbish.plex.direct:32400 making use of some DNS rebinding tricks. Your Plex server will be listening on HTTPS with a valid cert named like this. In most circumstances, this’ll work… but I don’t have remote access enabled, nor do I want to enable it.
If you start the app without settings -> remote access enabled, the app will try and connect to a custom server URL defined at settings -> network -> custom server access URLs, this URL must be HTTPS, so for example mine is set to https://plex.mydomain.com, and if I load that up in Chrome on my network, it serves Plex fine (because i have Plex running behind a loadbalancer on 443 using a valid certificate).
To figure out what Plex is trying to access, I looked at the DNS queries made from my PS5 to my DNS server, and saw that plex.mydomain.com was being queried when remote access was disabled, so this is a good place to look to see where the app is trying to load Plex from. Next once Plex is asking the right server for Plex content, I then viewed the network traffic to verify that Plex was talking to the right service on the correct port.
This would normally be enough info, but for me it still was not working. So I proceeded to look at the network traffic between the Plex HTTPS reverse proxy and the PS5 and I saw that the app was trying https://plex.mydomain.com but was failing to connect as I has set the minimum TLS version to TLS1.3, the Plex app does not support TLS1.3, once I lowered that to TLS1.2 it all worked fine.
I’m extremely disappointed in the lack of documentation from the PLEX team on how to troubleshoot this as its clearly been plaguing users for well over a month. The lack of error information in the Plex app is completely unacceptable, we should not need to resort to this level of troubleshooting to figure out what is wrong. Am also rather disappointed TLS1.3 does not work but it is entirely possible that this is a PS5 limitation though I’d like to think Sony are better than this.
Hope this helps.