Hi @emersyn, thanks for reaching out to us.
Interesting situation you’ve got there! VPP apps can still be pushed to the devices even if App Store is blocked on the device end, like @corbyn pointed out. However, built-in apps like the Calendar app won’t be available in the Apple Business/School Manager portal to be pushed as VPP apps. The sensible solution here would be to remove the App Store restriction on that particular device temporarily and then install the Calendar app from the portal before reinstating the App Store restriction again.
To prevent situations like this in the future, navigate to Policies > iOS > Advanced Restrictions > Allow App Settings, uncheck the Remove system apps option and associate the policy with your target devices. This will block users from removing built-in system apps like the Calendar app.
Please note that the Remove system apps option is supported only on supervised iOS 11.0+ devices.
Hope this helps.
Cheers!
Chris Wheeler
Hexnode UEM