The app@sharepoint principal is not resolving in newly created tenants

Quantumrunner 

I think I finally have the solution for it!

The tricky part is, that you have ONE term store per tenant, but it behaves independently depending on how you access it  (I mean, depending on the context of the site collection you are accessing it from)

https://MyTenant/SiteCollection01/_layouts/15/termstoremanager.aspx

and

https://MyTenant/SiteCollection02/_layouts/15/termstoremanager.aspx

and

https://MyTenant/_layouts/15/termstoremanager.aspx

both point to the same term store but differently from what you could expect, they don't behave exactly the same.

After reading this:

https://sharepoint.stackexchange.com/questions/168160/what-is-sharepoint-app-principal-shown-in-appprincipals-aspx-and-what-created-it

I found out the app@sharepoint is created when you add an app file and 'approve' it.
If you add the app file one sitecoll01 and then go to term store using the sitecoll02 URL it won't exist there... but will exist on sitecoll01.

In my case, we were adding the app file to many site collections, but accessing the term store based on the root site collection https://MyTenant/ Is the same term store, ofc. But the account doesn't exist there.

Go figure...