I am not able to tap with my touch pad

Hello, I am using hp compaq CQ61-225EE laptop with a synaptics touch pad version6.5. my touch pad was working fit untill today when I tried to use it reset of the functions were working okay but I can't tap(select) anything by tapping the pad. the left and right select buttons are okay and if I attach an external mouse its also working okay. Kindly reply as soon as possible. I will be waiting for your reply.