Although Tappan brand gas and electric ovens vary by model and design, you can break down the self-cleaning ovens into two types: models with a manual lock lever door and models with an electronic lock door. No matter the type, the oven door locks and unlocks based on two factors: the end or interruption of the self-cleaning cycle and the reduction of the interior temperature to non-harmful levels. Typically, if the door won't unlock, you haven't waited long enough for the oven to cool, or the oven control panel has malfunctioned.
Wait at least one hour after you have canceled the self-cleaning cycle, or it has ended on its own, for the oven to cool before trying the door.
Open the door once the oven has cooled. If you have a manual lock oven, slide the lock latch to the side opposite the locked position and pull open the door. If you have an electronic lock oven, simple pull the door open.
Check that the "Lock" light, or similar light or indicator, on the control panel has turned off and the clock indicates the current time, if you still can't open the door. If the locking light/indicator remains on or the clock is stuck on the countdown timer, try the self-cleaning cycle "Cancel" key on the control panel. If that doesn't unlock the door, try resetting the clock to see if restoring it to the current time instead of the countdown timer unlocks it.
Unplug your oven to perform a "hard reset" of the control panel if it appears to have malfunctioned. Wait five minutes, plug the oven back in and try the door again.
Start a new self-clean cycle if the door remains locked. Allow 15 to 20 minutes of the cycle to pass and then cancel it and wait another hour for the oven to cool. Try the door again.
Contact the Electrolux Group or a Tappan-certified repair technician for assistance with evaluating and repairing the control panel and/or door if you still can't open the door after troubleshooting the situation on your own.