1 if you have your wacom conected to a usb CLOSE to the usb of your mouse change the ports, and put the cable of your wacom in another usb port.
2 Deconect your mouse, and start to work with your software, check if the pressure work.
3 Go to the options of your wacom in your system, anc change the pressure options, or the INCLINATION, its very important!!!
4 i dont now wich software you use, if its photoshop, go to the temporary cache, and put the cache memory in another partition, restart your software and check if its working.
do you have new or old computer???