This happened to us also.  I found the apps in question were no longer available in the new iOS 11 app store.  Even though they're still listed in VPP and Meraki, the apps won't push to iPads with iOS 11 if they're not in the app store, even if the app store is disabled on the device.  Checking the app store on an iOS 11 device is the fastest way to see if the app is available on iOS or not ... View more