AD Connect: Azure Service Connectivity failed

Hey guys,

This article will be very short and focus one of troubleshooting I faced over the last week when I should have re-installed the AD connect for certain reason.
over the installing, as you know the wizard, I’ve provided the Global Administrator and on-premises Domain Administrator user,  post these wizards I got the following errors:

Azure Service Connectivity failed, Unable to Procced:
The on-premises synchronization service is not able to connect to Azure Active Directory, Updating the proxy settings for thr ADsync account may reolsve this issue.


ADSync Service Account Pelegit\AAD_38424d15cfd9

Extended message: Value can't be null
Paramenter name: DomainOrPrincopleName.

The issue was that this user: AAD_38424d15cfd9 hasn’t UPN in the on-premises AD:

As soon as you have set it, close the wizard and re-run it from the beginning, and then it will work.