Main oven wont come on or the light but the fan does

Hi, I hope I can help you. If you're referring to the overhead fan above the oven, that fac is usually on a separate circuit. The oven itself is connected to a separate circuit breaker, hence, that is why the oven and light won't come on.
Check your circuit breaker box, and see what circuit has tripped. Check to see if there are any burn marks around the breaker before resetting it.
The reason the breakers may trip, is the breaker is old, may have the incorrect rating, or may be linked to other circuits, such that when too many items are all drawing power at once, it will trip the breaker.