The cause is one of the followings. 

 

1

Smartphone's Bluetooth function might be turned OFF. 

Please turn ON the Bluetooth function via smartphone setting screen.

2

The door might be closed or locked.
Please make sure that the door is opened and the key is unlocked while registering a smartphone.

3

When forgetting family code, it can be checked by opening 「My Entrance」 →  「≡Menu」→「Digital lock setting」→「Family code」 on other registered smartphone. (Family code will only be displayed when smartphone is in transmission area）

When every registered smartphone is lost, making it impossible to check the family code, it is possible to delete registration data of every device.
How to delete all registration data

 

 

4

There might be an abnormality in door's power source.

【When using batteries】
Please reinsert batteries in correct manner or change the batteries.
How to change batteries

【When using AC adapter】
Please make sure that the AC adapter is connected with the power outlet.

【When using controller unit】
Please make sure that controller unit's power is turned ON.

5

When unsure of how to register, please check the link below.
How to register via application