Make sure that all your connections are good. Flexwatt will heat up VERY fast and it will get very hot. I'm not sure how hot it gets, but I know it says 120 degrees on the insert. Take your herpstat off and plug the flexwatt into the wall. It should get really hot within seconds. That will tell you if your flexwatt connections are bad, or if your herpstat is bad. I wouldn't be surprized with either.