Managed Apple IDs cannot be used to download apps; instead, Device-Based Assignment must be used.
Managed Apple IDs are not permitted to be used in any commercial transaction. This implies that IAPs, storage or service purchases, as well as app purchases, are no longer available. Apps may be distributed via Device Based Assignment. To compensate for the inability to purchase more, Apple has increased iCloud storage restrictions. There is presently no workaround for IAPs; you will need to contact the app creator for alternatives. To deal with this scenario, several apps provide a full-featured version.