If your old and new keys are both working after a rekey, here's what to do.
First, confirm the step change took place. A small metal wafer will drop out (pictured on the rekey kit card). If a lost rekey kit is being bypassed, the rekey instructions must be repeated for each step being skipped.
A rekey requires a full 180 degree rotation with the Step Change Key. If your lock hardware keeps the lock from turning that far, a Control Key is needed to do the rekey in hand and then the core can be reinstalled in the housing.
**IMPORTANT: If you do not have a Control Key in the rekey kit being used, DO NOT REKEY.** There is a unique Control Key for each step change, so if a Control Key from the current step is used to remove a core and the rekey is done, the core cannot be reinstalled without the next step Control Key.