If the switch is off, there is no power to the oven.
There are two reasons why this switch (circuit breaker) is closed. One is because it was turned off by someone in the house.
Or, it could be shutting down because something in the circuit is malfunctioning, causing the safety switch to shut it off immediately
In either case, to fix this, simply go to your home switchboard panel and make sure the oven circuit is turned on.
If your oven isn't hardwired because it's gas or plug-in, just check the power point it's plugged into to see if the switch is on.