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, test it with a multimeter to see if it's open circuit.
If it is, you need a new element.
Swap the wiring on to the new element.
Don't lose the wiring into the back or you will need to take the rear panel off.
Fit the element in place and replace the cover.
Turn the power back on and set the clock.
Try the oven again.
Hope this helps
Let me know how it goes or if you need more help
No, you need a multimeter to test the element with no power applied.
If the element is good you'll get a low reading in the ohms scale or the buzzer will sound for continuity.
If it's no good, it won't buzz.
A screwdriver tester will only tell you there is power of an unknown voltage at the point you are testing.