Hello, @Edwin Rombouts !
The relationship between Azure tenants and subscriptions is one of our most common points of confusion for those who are new to the subject and I appreciate you following up with the resolution.
As you pointed out, an Azure Active Directory can have one or many Azure Subscriptions but an Azure Subscription can only have one Azure Active Directory. If you create a new Azure Active Directory tenant, you'll need to associate your subscription with your new Azure AD directory tenant:
- Sign in and select the subscription you want to use from the Subscriptions page in Azure portal.
- Select Change directory.
- Review any warnings that appear, and then select Change.
- Select Switch directories on the subscription page to go to your new directory.
Tenant/subscription relationships
Changing the directory of your subscription
Additional Resources