I've got an issue with a pilot deployment of iPhones with VPP device licences assigned. These are iPhone 11s, running iOS 13.3, managed via a MDM solution that pushes VPP device licences to DEP managed devices that are enrolled into the MDM.
All sets up well and fine, and the user can take a fully deployed iPhone and sign into the MDM solution's management app, and then the Apple App Store works just fine. All the apps we push appear as expected and the iPhones work as expected.
However, some users are prompted daily for their (managed company) Apple ID if any application updates are pending for the apps that were pushed to their phone using VPP (Just to be clear, the user is being asked for their own managed Apple ID, not another person's Apple ID or the VPP token details).
It looks like this is related to automatic app updates, as these prompts cease if this is turned off in iPhone Settings app → iCloud → iTunes & App Store → Automatic Downloads → App Updates.
Expected behaviour should be to update the apps without the user having to sign in again.
Note that the VPP apps are correctly licenced to the device, and its possible to deploy a device, hand it to a user who does not sign in to the App Store, and app updates are pushed just fine.
Best Answer
If anyone else experiences a similar issue, I've just had a discussion with Apple and they have confirmed this is an issue in iOS 13 and that it is fixed in iOS 13.3.1