Signed up for the 30 day trial.
Running Server 2012R2. Downloaded and installed the mskecert which is part of the Windows 8SDK.
Generated the certificate and uploaded to Azure - all success. Verified - working.
When I go to register the server via Windows Backup, it fails with the Certificate is not associated with any backup vaults. Right now, the server is on my local lan. No proxy. No firewall. All patched and up to date. Verified through MMC that the certificate exists in the Personal and Trusted Certificate store.
Looked at the logs and nothing jumps out either.