Issue fixed by firmware v1.80:
When using lens and TC combinations with max aperture smaller than F5.6 (such as EF100-400/4.5-5.6L IS II USM + 1.4X or 2X), AF was not available.
![broken image](http://custom-images.strikinglycdn.com/res/hrscywv4p/image/upload/c_limit,fl_lossy,h_9000,w_1200,f_auto,q_auto/975448/849345_720808.png)
Please download the new firmware and release notes from here. Follow the instructions in the release notes to update your adapter.