error code "0x87D13BA9"

Nathan7876 

The key here is the difference between iOS apps that are VPP versus direct iOS App Store apps, and the difference between a Device Enrollment versus a User Enrollment.

A VPP app is one that is added from Apple Business Manager and is listed in Intune with the App Type of “iOS Volume-Purchased Program”. It syncs automatically to Intune once added to Apple Business Manager. VPP apps can only be assigned / installed to iOS devices enrolled through the Device Enrollment process.

An iOS App Store app is added directly in Intune and is listed with the App Type of “iOS Store App”. iOS Store Apps can only be installed on devices that are user enrolled. You cannot assign a VPP app to a device that is enrolled through User Enrollment.

My guess is that you have enrolled your device with User Enrollment but are trying to assign a VPP app to it. This fails with the noted error.

Microsoft should document this, for sure.