Inspect the fuse box or circuit breakers to ensure a breaker hasn’t tripped or a fuse hasn’t blown, if the oven won’t turn on at all.
Increase the temperature on the control panel, then wait for the oven to rise to the temperature you want.
Remove some of the pans you placed in the oven, so you have fewer pans in the oven at one time.
Wait for the oven to preheat to your desired temperature before you add your food.
Close the oven door completely, and keep it shut during the cooking time, so the heat remains constant.
Make sure the gas supply valve to the oven is all the way on.