Claiming the server doesn’t work like that anymore: New Claiming Requirement for Windows
Careful to use a regular web browser without 3rd-party browser add-ins.
Ensure that you have installed the 64bit version of Plex Server. (the binaries should be in C:\Program Files\Plex\Plex Media Server
and NOT in C:\Program Files (x86)\Plex\Plex Media Server)
The installed app is called “Plex Media Server”. If you only have an app which is simply called “Plex”, you don’t have the server installed.
https://support.plex.tv/articles/201941078-uninstall-plex-media-server/
