You might have to repeat the steps I wrote in my first response above.
But first, do the following:
- Quit Plex server
- open the ‘services’ control panel (just hit the Windows key and start typing
services, it has this ‘cog wheel’ icon) and stop the service named ‘Plex Update Service’ - download the attached
.regfile, unzip it and double-click it. (it just disables ‘Secure Connections’ in your server configuration. You can use a text editor to check its contents.) - reboot the Plex server machine