If a data point helps, I just did a reset. The process to reclaim my Windows based server was a little convoluted. I visited http://localhost:32400/web and after signing into my plex.tv account, I was able to see my personal profile settings but the server wasn’t in the dropdown, not even listed as “offline”. (Aside: I use a System Tray service to run Plex in the background as a service-account user, so normally my profile shows two claimed servers, the regular one that runs under the service account and a second “empty” one that has a data directory under my regular user account. The “empty” one showed up but the regular one was missing.)
I skimmed through this post and one of the suggestions was to find the Plex Media Server data directory, and open the Setup Plex.html file there. When I did this, I was prompted to authorize against my plex.tv account again, then it took me back to the settings page and this time I could see my regular server in the list, already showing as claimed.
I don’t know if this works on other platforms, but at least on Windows you should try Setup Plex.html from the local filesystem, I think it basically runs the claim process described in the posts above (getting a token and passing it to your local webserver) automatically.
