My MCO 160UB microwave which is 4 years old will not heat up. Some of the settings say -20, -1...is there a way to reset the microwave so I can get it to heat up. The power level is 10 and when you hit time cook it will run but will not heat up the food. My wife used it to heat up soup prior to attempting to use it a second time and it heated the food with no problem.