Your digital lock has no battery :-).
Your phone charges the lock
Your phone is needed to charge the lock with your NFC chip. Then you can open or close the lock.
Keep the phone very still
To charge the lock you must keep the phone very still other wise you will get 'access failed, try again'.
The NFC scan area is on the top of your iPhone.
You will hear "click from the lock" and see "Access Granted" on your phone. Then you can turn the black knob. You have 15 seconds to operate the lock.
Watch the video below then try again and you will see it will work :-).