I have a Kenko tokina 1.4 teleconverter. When attached to 150-600mm C sigma lens and camera switched on, it shows Err01. However if the electrical contacts of the teleconverter are blocked with a tape the lens and teleconverter operates Manual. The same teleconverter works allright with a canon 70-200mm L lens with autofocus options. Tried all techniques to overcome Err01 error. Did not succeed. So which brand of 1.4 teleconverter offers autofocus.