Hi,
What version of Mathematica are you running? You will need 11.0.1 to use the SenseHAT driver. You may need to update your Raspian to use Jessie over Wheezy, which only supports 10.0.2 and doesn't include the SenseHAT. Once you are running under Jessie, you can then update Mathematica with:
sudo apt-get upgrade wolfram-engine
Thanks,
Ian