Scratching on my DDJ SR

ok, when I try to scratch on my DDJ SR, there is no response, but when I put my hand on my laptop and try and scratch it works! I need help solving this, I have a 13inch Mac book Pro 2013 and I'm on my 2nd DDJ SR, I took the first one back thinking it was a malfunction with the DDJ SR, but the 2nd one is doing the same exact thing. Help Please