Zanussi ZCG7700X Lighting the oven?

I have just moved into a flat with this appliance. The oven will not light. All the four gas rings on the top and the grill light when the knob is turned and the ignition switch is pressed. When I turn the knob for the oven I cannot hear the gas flowing, which I can with the grill. The ignition works in the oven - I can see the spark.
The instruction Manual pdf will not download - so no help there.
Can anyone help?