Homw Screen won't sleep

[CFreeman1]

Last night my HTC One SV phone stayed on and won't 'sleep' Obviously this is draining my battery. I've tried turning off then on to no avail. Can anyone advise me as to how I resolve this problem please?

 

[B. Diddy]

Welcome to Android Central! Try installing Wakelock Detector, let it run for a few hours, and see if there are any apps listed that are causing a full wakelock.