Hello. To go 12 years without issues is excellent. Now however you will have to make a decision to repair or replace. Be sure to get a firm estimate before you repair and compare that to the cost of replacement.
here is what may be causing your problem:
Usually when an oven won't bake, it's because the bake igniter is weak or burned out. The igniter is a small, round or rectangular device, that's about 1 inch by 4 to 8 inches. It's near the burner itself.
The burner is the tube-type device the gas flows through before it's ignited. It has many small holes on the sides to let the gas, when ignited, form a long, low flame. If the igniter is weak, if it glows red but doesn't get hot enough, or if it's burned out, the gas doesn't flow to the burner and the burner won't ignite. If this is the problem, you may need to replace either the igniter or the gas safety valve. Usually the igniter is to blame.
Other reasons that your oven may not bake are:
- The clock settings are incorrect (if you have timed baking or a self-cleaning oven).
- The thermostat is defective.
- The safety valve that prevents accidental gas flow is defective.
- The selector switch is defective.