OVM-1004 XML-RPC Client Call Oracle VM Agent API 'register_server' error: exceptions.Exception:method "register_server" is not supported, please try again later.

If you get this error when you try to create a new server pool, then you are probably using two different versions of VM Server and  VM Manager which are not compatible. Look! error is misleading. This won't get resolved even if you try again a bit later, until you  have right packages installed.

Click here to see how I found this out.