Shut down Plex server using its trask tray icon.
Go into the Plex data folder, into the subfolder Cache and delete the file cert-v2.p12
Perform this procedure: You need to reclaim your server, but don't dare to touch the Windows Registry
Make sure not to use any 3rd-party firewall or anti virus software. Do also disable any web browser add-ins or ad blockers in the network/router.
