Hi,
This needs live troubleshooting. Since you have Azure AD premium, Azure support can help.
If you have access to azure support, please go ahead.
Else, please send an email to azcommunity@microsoft.com with your subscription id. Include the thread url in the email
In the email subject add "for jakaruna-msft - Can't activate Windows 10 via Subscription in Hybrid Azure "
I will enable a one time free support ticket for you.
Once your issue is resolved, Then you can post the resolution here and click on "mark as answer"