I had something similar happen to me just recently. I updated my iPhone to 8.1.3, and started getting the 'application could not be verified' error message from Xcode on an app that installed just fine on the same iOS device from the same Mac just a few days ago.
I deleted the app from the device, restarted Xcode, and the app subsequently installed on the device just fine without any error message. Not sure if deleting the app was the fix, or the problem was due to "the phase of the moon".