Please try the following methods:
Check if the batteries are drained.
Check if the lock has been paired with an existing account. If yes, please use that account to log in the app and remove the lock from within the app. Then, you can use another account to pair the lock.
Check if the lock has been reset.
While resetting the lock, you must hear one beep (indicating reset is done).
While pairing, hold the mobile device near the lock as close as possible.
Check the mobile device version.
Check the Bluetooth support of the mobile device.
Turn off Bluetooth, and then turn it on again to retry.