Microsoft Store analytics API call fails with "User Unauthorized EC2"

Question

Our calls to

https://manage.devcenter.microsoft.com/v1.0/my/analytics/installs

Have started failing with a very strange "User Unauthorized EC2" error. These calls have been working for years.

We originally followed https://learn.microsoft.com/en-us/windows/uwp/monetize/get-app-installs

We are able to successfullt obtain a token:

https://learn.microsoft.com/en-us/windows/uwp/monetize/access-analytics-data-using-windows-store-services#obtain-an-azure-ad-access-token

but when using that token it fails with the above error.