Error in title appears when attempting to add a desktop to DaaS. This issue is most commonly seen when expanding an existing pool or creating a new pool. By default, in Active Directory authenticated users can join up to 10 computers to a domain. Administrators can join as many computers as necessary to a domain.
Option 1 is to add the service account used to join computers to the domain for the DaaS tenant to the administrators or domain admins group.
Option 2 is to try one of the three methods provided from the following Microsoft KB article.