NOTE: This post – drafted, composed, written, and published by me – originally appeared on https://blogs.technet.microsoft.com/johnbai and is potentially (c) Microsoft.

To get around this, add the permissions by following this article for pre-staging the Cluster Name Object for a Database Availability Group. If you still receive the error, modify the ‘dNSHostName’ attribute to reflect the FQDN of your DAG, as referenced below from my lab (suffix removed from screenshot):