MS is lacking proper documentation on this, as well as things not being named right, etc, at the time of this post.
In order to add an MPN ID to an app registration, you need to know and provide the following:
- MPN ID is no longer named such, it's now called a Partner ID
- MPN is no longer called Microsoft Partner Network, it is now called "Azure AI Cloud Partner Program"
- Having a Partner Center account is not sufficient, you must also go to Account Settings/Programs, and specifically add the "Azure AI Cloud Partner Program"
- Partner ID is now accessible in Account Settings/Identifiers/Azure AI Cloud Partner Program
- You will probably notice TWO Partner IDs. You need the one of type PartnerGlobal
- HOWEVER... You still cannot add this ID to your app registration! First, you MUST:
- Go to Account Settings/Tenants
- IMPORTANT: if you are in multiple programs, you might see multiple tabs at the top, such as Partner | Developer. Chose the tab/program you want to actually associate your app with (the Entra that has your app registration)
- Now click "Associate Microsoft Entra ID" to link your other tentant in here. * you will need to sign in using a global admin account of that particular tenant - see below.
In my case, our Entra tenant was a DIFFERENT one than what was associated with my Workplace account I signed into the Partner Center with. But when I tried to "Associate Microsoft Entra ID" from the tenants area, and sign in, it would fail (could not validate you as a global admin), even though the current auth user of the Partner Center was a global admin in both tenants. I had to make a local user in the tenant that has my app, make them a global admin, then in the Partner Center, Associate that Entra, which makes you sign in... and be sure to auth with that local global admin user you just created in order to "find" and confirm the link. Partner Center should then, finally, let you add your tenant. And NOW you can go back to your app registration, add the PartnerGlobal Parnter ID into the "MPNID" field, and it should link up without the annoying MPN Account Not Found error.
At the time of this post, Microsoft has a LOT of improvement to make. First, the issue that App Registration is still referring to "MPN ID", which is no longer the proper naming. And that it does not tell you, AT ALL, how to get that ID or where to go (not even so much as simple support doc to outline everything I just did here). And last, the fact that Partner Center makes you use a MS account rather than a Workplace account in order to join the Developer program is just absolutely stupid and nonsensical.