[RH318 Course] I can't import rhev-h

Hi everybody~

RHEVM Events Log : 'host registration failed, empty host'(id 843)
It occur when I try to import rhev-h(servera) into rhevm.

rhevm Web Manager log is 'host registration failed, empty host (Host:172.25.1.10) - id 843

and /var/log/ovirt-engine/engine.log is...
WARN Custom Event ID: -1, Message: Host registration failed, empty host id (Host: 172.25.1.10)
ERROR (ajp-/127.0.0.1:8702-8) Query execution failed due to invalid inputs. Cannot register host '172.25.1.10' - host id is empty.

I don't know reason this issue.
Who knows how to solve this problem?

Thank you.