Set all this up before you move to the network without internet connectivity.
On PMS disable secure connections and add the network you’re using to the ‘allowed networks without authentication’. You may be able to just use 127.0.0.1 since it’s on the same box.
On OpenPHT enable auto-login. This will save your plex authication token.
Then pull the plug and login & reboot a couple times to see if it’s going to work.
