When you enable the Kisi Reader Restriction, it requires users to be within the range of a Kisi Reader to unlock a door. You can enable reader restriction for individual doors (everyone trying to access the door will be affected) or groups (anyone in the group trying to access doors for that particular group will be affected).
The Reader restriction requires that all users enable: Bluetooth, locations services, and (Android only) NFC. Users must be within the Bluetooth range of the Kisi Reader outside of their door in order to unlock the door.
When users receive unlock errors
The Reader battery could be flat (battery readers only), Bluetooth and Location Services may not be enabled. Also, it is possible they are not within range of the reader.
This restriction is beneficial because it only allows for unlocks when the user is right by your door. It is more targeted than the Geofence restriction.