Since you had a power outage, you possibly have a circuit board issue. Try unplugging the heater for a couple of minutes then plugging it back in. If that doesn't help then a new circuit board may be needed. There are 2 different circuit boards. One main circuit board and one for the display. I hate to inform you of this but this are both very expensive. The main board will cost somewhere around $400. I'm not sure of the cost of the display board. If you have someone replace them, have them do to one and see if it fixes it. If it doesn't, put the old one back and replace the other, that way you can narrow it down to 1 or the other. There is a place in Ashville, NC that will repair monitor circuit boards. http://www.mathiselectronics.com/product-services/Monitor-heater.html
Go to this link and it will give you prices for the repairs. They guarantee their work for 3 years. If you contact them mention you heard about them from Niten's Heater Service. Sorry I can't be more helpful.