This issue is seen in devices with iOS 11.3.1 and 11.4 where users have enabled “Use Touch ID for iTunes and App Store” in Settings (see screenshot) and you want to deploy iOS store apps with assignment types 'Required', 'Available for enrolled devices' or 'Available with our without enrollment'.
When installation is attempted for Intune-managed store apps deployed as above, a Face ID/Touch ID authentication prompt appears, attempts authentication a few times, and eventually fails with the message “The <app name> could not be installed”.
We have determined that the root cause for this issue is an iOS bug. Apple is aware of the issue and we will keep this page updated as we know more.
Until this is fixed, if you wish to deploy apps as ‘Required and Available’ on iOS 11.3.1 or 11.4, please ask end users on those devices to temporarily disable the setting 'Use Touch ID for iTunes and App Store'.
Updates:
7/30: Updated to clarify assignment types