The lock does not respond when a card or code is presented. What should I check?

Work through these four checks in order:

1. Confirm the lock is not in a temporary input-suspension state caused by repeated rejected credentials — wait about a minute and try again.
2. Confirm the battery is not low or exhausted.
3. Confirm the credential is valid for that specific locker; in public mode, a card is only accepted by the unit that it locked.
4. Confirm the card is MIFARE-compatible and undamaged.

If all four are correct, open the locker with the master key and contact support.