Temperature rises but does not reach the set point:
1) Check the thermostat. This includes the thermostat's heating output status, output power ratio setting (if the thermostat has this function), the thermostat's temperature compensation setting, the thermostat's over-temperature setpoint action and setpoint, and the PID parameters (refer to the factory settings).
2) Check the heaters and heating control circuitry. Some ovens use multiple heating groups. Check that each group is functioning properly. Use a clamp-on ammeter to measure the current in each phase of each heating group, or disconnect the heaters and measure their resistance.
2. Temperature does not rise or heating occurs:
1) Check the thermostat's status indicators and settings.
2) Check the heaters and control circuitry, including whether the AC contactor is properly engaged, whether the heating circuit breaker is open, and whether the intermediate relay is functioning properly.