To be clear an MS account is different than your MSDN subscription (now known as Visual Studio Subscription) which is different than an Azure account. A VS subscription requires an MS account. An MS account can technically use any email address you want. An Azure account is an MS account that is tied to Azure. For that to work you generally have to set up billing information and then you'll get your own subscription to work with. VS subscriptions give you Azure credits so often they are the same thing.
Dev Box currently requires, based upon the docs here
- Entra ID which is an organizational thing (Entra ID P1 to be specific)
- Microsoft Intune which is an organization feature
- Windows 11 Enterprise license (which your VS subscription may or may not have, depends on your subscription level)
- Active Azure subscription
Your personal Azure subscription won't have all that. Hence you would need to use a work account associated with an organization using Entra and Intune in order to use dev boxes.