No batteries in the remote control, empty batteries or batteries not installed correctly.
Ensure batteries are installed according to the illustration in the battery compartment. If they are, replace the batteries using two 1.5 V AA batteries (type R6). When using rechargeable batteries, the range of the remote control will be reduced due to lower (1.2 V) voltage. Rechargeable batteries auto-discharge and thus deplete more quickly.
Note: