whirlpool akz151/wh eletric oven?

I have a whirlpool akz151/wh eletric oven, built in and the digital readout is displaying the word "stop". This came about after an electricity power cut. I've tried depressing the middle button (timer button) for more than 10 secs in the hope that I can reset the clock and thus free it but it hasn't worked. I've tried turning the power on/off and pressing/holding the timer button again and again but it is still reading "stop" and won't allow me to select any of the functions and therefore the oven cannot be used.