Have you tried cycling the AF mode switch back and fourth a few times? You should also try cleaning the electrical contacts on the camera body, both sides of the TC and the lens. Make sure all of the contacts are projecting out the same distance. They are spring loaded and can get jammed in. You also might try rotating the lens and TC back and fourth to make sure it is not an alignment issue with the electrical contacts. Good Luck and Enjoy your Nikons!