iPhone6 ios 9.2 will not remember my fingerprint

[KatherineNYC]

I spent many days with tech support including getting a replacement phone. No matter what I do, my phone does not remember a finger print for more than a few hours and definitely not overnight. The phone has been restored as new in a manner that should have prevented any software glitches from being restored to the phone. Moreover, the fingerprint reader had been working for nearly two months straight. (Mostly, it has not worked for the 1.5 years I have had the phone). Very frustrating. And, I do not see a thread on this issue (maybe I missed it?) for 9.2.