main oven will not light and ignition will not operate?

Hi,
We had a Cannon Camberley double oven cooker, it was working
perfectly but decided to update to a newer model, we sold the
Camberley on only for the new buyer to tell us the main oven
is not working, the gas will not come through to the jets in the oven, also the ignition will not work.
The other parts of the cooker are working normal, hobs and the top oven,also the ignition works as normal on these parts!!
Can anyone help with what is causing this problem please.