I recently moved my media over to a different pc to host my Plex Server on that. I removed the server from the list by clicking the X and following the prompts. However, on the new PC I cannot claim my new server. It just keeps spinning on me. I log out and then it cant reach media. I dont know what I did. I did not have any issues on the previous install.
if you’ve already tried this - https://support.plex.tv/articles/218136308-why-is-there-an-unclaimed-media-server-on-my-network/
check the IP address range of your new server - Can't Claim Server
Also - make sure you clean cookies from browser, log out of PMS everywhere.
Did all that, no luck 
Same situation with me. I have logged off and back on sever times. Downloaded a different browser, same result. Pressing the Claim Server button does nothing just sits there spinning
