When you try to use the appliance, does the temperature light on the front come on?
As the fan is running and the temperature light is coming on, then the most likely cause of the problem is a failure of the circular element in the oven.
Isolate the power to the appliance.
Take the rear panel inside the oven out.
This will reveal the element and the fan.
Take the screws holding the element in place out.
Bring the element and the wiring into the oven cavity.
If the element is not obviously blown, you need to test it with a multimeter to see if it's open circuit.
Swap the wiring on to the new element. (Don't lose the wires into the back or you'll need to take the appliance out and remove the panels to retrieve them).
Fit the element in place and replace the cover.
Turn the power back on and set the clock.
Try the oven again.
If there are no screws holding the element in place, take the oven out and take the rear cover off.
You can now access the wiring and the nuts holding the element in place.
Hope this helps
Let me know how it goes or if you need more help