iMovie is not working on my shared managed ipads in school

We have purchased IPADs for school and have them set up on a MDM as shared devices. When we try to open iMovie it wont open. It is coming up as an unmanaged app on the devices. We have purchased licenses (Apple School VVP) and tried to install but an error bounces back that the app is already installed. The same is true for garageband. How do we fix this?