IS this a straight shaft or curved???? If this is the clutchless design the cable usually is square on the ends. I probably is not fully connected at one or the other.

IF it's got a clutch then you won't be able to feel it when it splines in cause the clutch will free spin till enough RPMs to engage it.

Did you have it disconnected at the engine end? If so it may not be engaged into the square hole. Before I assemble it I slide the lower Rod assy into the engine end and then I turn the string head. you can feel if it is connected or not. If not pull the cable out it maybe twisted off at either end.