Domain credentials are not included for the Clean OS recovery method, which is required by the health check to authenticate.
Clean OS only asks for the local machine credentials of the target.
WORKAROUND
You will need to create a new Forest Recovery project, and connect to the newly created forest.
Set the restore method to anything but "Clean OS", as this will prompt for domain credentials.
Once domain credentials are entered, you should be able to perform a health check.
STATUS
Waiting for fix in a future release of Recovery Manager for Active Directory Disaster Recovery Edition.
