GE Conv/Micro just stopped heating either way. All else works.
One hot dead
A typical big oven (as opposed to a countertop/portable oven) in the US uses 240V for heating (possibly including microwave) and 120V for controls/lights/fans. The power is connected (ideally, not always due to "old stuff", among other things) with 2 hot wires, 1 neutral wire and 1 ground wire. The 120V items use one hot + neutral. The 240V items use two hots. If the hot used for 120V is good but the other hot is out, then controls/lights/fans will work but you won't get any heat.
Check your circuit breaker. A 240V/120V oven should be on a pair of breakers. They definitely should have common shutoff (i.e., if you manually flip the breaker off, both hots are disconnected at the same time) but they might not have common trip. So turn the pair of breakers off/on and see if that helps. IF YOU DON'T have a PAIR of breakers side-by-side, STOP and don't do anything else without posting some pictures to diagnose some more.
If resetting the breakers doesn't solve the problem then you likely have a loose connection somewhere:
- Wires coming out of oven
- Wires going into plug (if it is plug/receptacle rather than hard-wired)
- Wires going into receptacle (if it is plug/receptacle rather than hard-wired)
- Connection between wires coming from oven and wires from breakers in a junction box in the wall (if hard-wired)
- Wires going into breakers
Before working on ANY of those wires, turn the breakers off.