There are a couple of things that you can check;
1) Make sure the subwoofer output is enabled in the amplifier set-up menu.
2) Make sure your connections are correct - subwoofer Pre-out (from the amplifier) to left line in on the subwoofer.
3) Make sure the Auto switch on the back of the subwoofer is set to the 'On' or 'Auto' position.
4) Check that the volume on the subwoofer is not set to minimum.
As a double-check, you can make sure that the subwoofer is connected using the left line-in input, and with the other end of the subwoofer lead, disconnect from the amp and touch the end with your thumb. This will send a signal to the subwoofer (you will hear a dull thud from the subwoofer with each touch), which should show you whether the sub is working or not.
If none of this helps, then we would suggest contacting your dealer to arrange for an inspection of your equipment.