From what I’ve read on Stackoverflow, if a device runs IOS 8 it’s no longer possible to install and sync provisioning profiles and apps to the phone. Instead, the dev should invite testers on developer.apple.com via email, and the user should install the TestFlight IOS app and respond to the invite.
If so, there should be a note here: https://docs.coronalabs.com/guide/distribution/iOSBuild/index.html#distribution-ad-hoc
Can you confirm that Corona will include the correct metadata automatically in the app for testing, as described here, if a distribution profile for app development is generated? https://developer.apple.com/library/prerelease/ios/documentation/LanguagesUtilities/Conceptual/iTunesConnect_Guide/Chapters/BetaTestingTheApp.html
This is the official page https://developer.apple.com/testflight/
This shows the steps https://itunesconnect.apple.com/downloads/Documentation/TestFlight-v09-iTC-Export-sw.mov