Did you switch routers or ISPs recently?
Most likely it has to do with ‘DNS servers’ or ‘DNS rebinding protection’
Both are defined in your router.
Usually, you set DNS server to ‘automatic’ so that is uses whatever your ISP tells it to use. Unfortunately, some ISPs mess this up and provide DNS servers which don’t handle the .direct TLD well.
So define your own DNS server. Use Google’s for instance (8.8.8.8)
DNS rebinding protection is normally a good thing. However, most implementations misfire at Plex’s (totally legitimate) use of the DNS system. Therefore one needs to define an exception for the domain plex.direct
After making changes in your router, it is best to reboot the router first,
then after a few minutes the Plex server
and after another few minutes all your Plex clients.
Do also check that
Settings - Server - Network - ‘Show Advanced’ - “LAN Networks”
contains the network address of your local network, e.g. 192.168.1.0/24
and that ‘Treat WAN IP As LAN Bandwidth’ is checked
After making any changes there, restart your Plex server and let it sit for a few minutes.
