The cause is one of the followings. 

1

The remote control's power might be OFF. 
Please press both buttons of the remote control for a certain duration to turn ON the power.

 

2

The remote control might ran out of battery. 
Please change to new batteries.
How to change batteries
If this does not solve the problem, please contact customer support.

 

3

An error might have occurred in remote control function due to static electricity. 
Please take out both batteries and reinsert them into the remote control.
 How to change batteries