Currently using Jamf as a managment solution for iPads in schools. I have licensed Adobe Scan through Apple School Manager and set up the app to push out to all iPads in the school. The specific user who requested the app, her iPad constantly says Device busy, will try again. She's connected to the internet, has been using the device this morning etc. There is no reason why this should be failing to even update the inventory.
Few things about app deployment...
1) make sure the device is charged to at least 30-33% 2) make sure the device is unlocked (i.e. passcode entered)
3) search for the device in Jamf. Under the Management tab, Send Blank Push, then Update Inventory
As long as the device is connected to an accessible network, where it can reach both Apple and your Jamf server, and it stays unlocked, the app should push to the device. If it does not, restart the device and try again. I've seen poor Wi-Fi also affect app deployment.