my ovens doent work?

You do not mention the make or model of your oven
You do not say just what you've done with the clock

But no matter...

The general case is that the clock gets accidentally set to auto timer mode.

To get the oven to work you need to reset the clock- switch off the main electrical power and switch it back on again so that the clock flashes.

Depress and hold in buttons 2&3 from the left and use the plus and minus buttons to set the time - any time will do.

If this fails to work then you may have a defective clock.

Good Luck...
February 2017