You should visually check the fan oven element for cracks and splits or check the resistance of the fan oven element for continuity. If it is cracked or split or not registering continuity then it’s failed.
Visual checks are done through the front cavity having removed the back panel. Continuity checks are done via the back with the rear cabinet panel removed.
In all cases isolate the unit from the mains!!!!
If it is the element then it’s available from the link below.