@Anri Cela Thanks for posting in our Q&A.
For this issue, I have done some research. I find that the app configuration policy supports these two type apps:
Managed iOS/iPadOS app from the app store
App package for iOS
https://learn.microsoft.com/en-us/mem/intune/apps/app-configuration-policies-use-ios
It seems that it doesn't support "iOS volume purchase program app". So, these apps aren't listed.
Hope the above information will help.
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