I can't speak from experience because I don't have the M8, but I've been reading up a lot on it here and there's a thread addressing it. From what I can tell, the t minute flash is an HTC thing hard set in the phone. There is a definite issue with it not flashing the LED at all too. There seems to be two ways around it.
The easiest is people are reporting to disable the Verizon Messenger app. That one wasn't well reported on either way, but several people that tried said that fixed it. Worth a shot first. The other is to factory reset and skip the automatic data/backup restores. Don't even sign into Google on the setup. After the phone finishes initializing the native apps, then manually download your other apps and such. A pain I know, but that was the more popular method and worked.