The server can say that if it’s unclaimed. Because the server and player are on the same PC, what do you get when you type this?
http://127.0.0.1:32400/identity
If it says claimed=0, then you should be able to (re)claim it.
If it says claimed=1, then it is claimed.
The document to read these days if you have to do so: You need to reclaim your server, but don't dare to touch the Windows Registry
