The cause is one of the followings. 

1

Key card/tag key might be swiped at the wrong area of the digital lock.
Please swipe the keys at the area with signal wave mark.（）

2

The door is either closed or locked. 
Please open and unlock the door before registering key card/tag key.

3

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.

 

4

The registration devices might be over the limit.
Up to 10 card keys/tag keys can be registered to 1 door in total.