You may occasionally find that your subwoofer won't power up, or won't produce sound, or will only produce a very soft sound. Here are some troubleshooting steps to isolate the issue, and what you can do to solve it.
It's not powering up!
At the risk of being rude...have you checked it's still plugged in? Maybe the plug's been bumped loose just enough to stop power flowing, or someone had to charge their phone and chose that socket to plug it in.
Check that the cable isn't at fault. SVS subwoofers use standard Figure 8 and IEC cables, both found commonly in household items like kettles, rice cookers, and other electrical equipment. Replacement cables are cheap and easy to find, if that's the issue.
It's not making any sound/only making a soft sound!
Check the connection to your amplifier or receiver and make sure that the cable is properly plugged in on both ends.
Check that your amplifier is set to output signal through its sub out or pre out, and that volume settings are at a suitable level.
Test your subwoofer by plugging a phone into its RCA inputs (you'll need a 3.5mm-RCA cable to do this, and the appropriate dongle if your phone doesn't have a headphone jack). Play music through your phone, preferably something with some tasty low end, to see how the sub responds. If the sub sounds normal, then the issue is with your amplifier or the source.
Still not working?
If none of these steps help, you may need a new amp module. Send your name, proof of purchase, postal details and the serial number of your subwoofer to us here to organise a replacement.