Must enter a valid code
I am trying to help get the iPads set up for a school, and I am coming across some issues.We are using MobileIron and Apps@Work. When downloading the Prepaid Apps, sometimes only one or two will start after clicking "Request", and then a message will pop up saying "You must enter a valid code". At that point, I cannot get the rest of the Apps to download. On some iPads, this message will pop up on the first App that I requested, and none of the apps will download.
I don't understand why this happens on only some of the iPads. I currently have about 4 out of 18 that are doing this. I am not well versed in iPads, so I don't know where to begin with this. They are iPad 4s.
iPad, iOS 8.4.1