the incline motor on my Nordic Track S3000 is not doing its job properly?

when I increase the incline from 0 to 15%, the treadmill raises no more than half an inch. The incline at 15% should be at least 9 inches high. I took out the motor cover to see what's going on. Each time I press the + botton to increase the incline, I hear and see the incline motor going, but only making small movements for a second or two. Not making enough turns to raise the platform to the proper height. What can I do to fix it. I thank you in advance.