Wait a mo - if you know the motor turns in the correct direction, do you mean that it worked previously and now will not start? The only other thing I can think of, other than a component problem, is that your throttle trim is set too high and the ESC will not arm, as it perceives that the throttle is partly open (instead of being completely closed as is need by most ESCs), and hence will not run the motor for safety reasons.

Just a wild guess, but worth thinking about...Chris