Bosch hbn 32 oven not heating up ?

I have a Bosch hbn 32 oven that is not heating up when switched on and the temperature is set as we would normally do.
The grill inside the oven area still works fine and the fan & also the oven light are both working.
The automatic on-off system to roast if you are out does not appear to be involved in the problem as it indicates in the oven instruction manual (eg there are no symbols illuminated on the display other than the time)
The oven was working fine this morning until we had a general power cut and then the oven did not come back on when the power cut ended.