If your multirotor has a slow spin, poor yaw control, or no response when attempting to yaw, there are several factors that may be contributing to this behavior.
To begin, ensure that your throttle range is set according to this guide.
Once this is done, examine your settings and aircraft.
1. Make sure you have the latest firmware flashed to your Hoverfly product with the correct mode for your motor configuration.
2. Ensure that you have the proper configuration of clockwise and counter-clockwise propellers.
3. Check that your motors are perfectly perpendicular to your Hoverfly product.
4. Make sure your fully loaded multicopter has approximately a 2:1 thrust to weight ratio. (Be sure to perform test flights with a dummy payload equal to the total load you plan to carry.)
5. Try lowering your overall gain. Yaw gain is tied directly to overall gain, and setting this number too high can cause the yaw channel to falter.
If, after performing the above steps, your multicopter still spins slowly, you can try tilting the motors a few degrees in the opposite direction of the spin. This should be done equally to ALL motors. Alternatively, tilting the CW motors right and the CCW motors left can increase the overall yaw authority of the aircraft.