If the both, broil and bake, elements are not getting red hot, then the problem most likely is a bad oven thermostat and/or the oven selector switch. Unfortunately both of them are no longer available.
You may want to check the circuit breakers for the oven and the wires inside the control panel and on the back of the oven. Otherwise it's time for a new oven.
Here are the breakdown diagrams and Replacement parts for General Electric JKP62G*K3 Electric range | AppliancePartsPros.com