As Joe says try plugging the UTH directly in without a thermostat just to see if it warms up. If it does check your thermostat. If it doesn't then the UTH is bad.

As for the 72 degrees on the cool side, I wouldn't worry too much about it for a couple days or even a week as when people are cycling temps for breeding some people cycle them down to that level at night and they will do it for a couple months!