I have an internally developed app that I am distributing with AdHoc distribution. I have an intranet page setup with an itms-services://?action=download-manifest link to install it on the devices.
The app is currently deployed to 20 iOS 6 & 7 devices. I tried to add 3 new iPod touches running iOS 8.
Here's what I did:
Added the UDID of the 3 devices list on the developer.apple.com site
Added the three devices to the existing distribution profile (which is valid for another 8 months)
Generated a new archive for enterprise/adhoc distribution with the xCode organizer (generates a new ipa and plist)
Tried to install the app on the new devices using the itms-services link
Two of the three installed successfully. The third one absolutely refuses to install. When I tap the link to install, the Icon appears on the springboard and it just says "Waiting..." underneath it. Nothing ever happens. If I reboot the device, this message pops up: "Unable to download app. "SAP-WM"(https://goo.gl/SoZGj4) could not be downloaded at this time."
I verified that the UDID is correct and that it is associated with the distribution profile (it is). I also tried factory resetting the device and starting over to no avail. I also successfully deleted and re-installed the app on one of the other iOS 8 devices to ensure that the archive was OK, and it worked fine.
Here's the output from the console of the device from immediately after I tried the install (notice the errors about the zip being invalid? makes no sense, it works fine on the other two devices!):