Ensure you don’t have any VPNs, or internet filters etc. activated.
It appears you need to perform this procedure: You need to reclaim your server, but don't dare to touch the Windows Registry
Notice the link on that page which explains the new method to claim a Windows server: New Claiming Requirement for Windows
If you still cannot claim the server, try to use a custom DNS server in your local network. 1.1.1.1 and/or 8.8.8.8 are known working examples.
