I've just received 2 pieces of Yongnuo YN568EX for my Nikon D610. When I’m on I-TTL mode the flash fires but the image is black (I tried it on each mode: auto, manual, A…), the sound tick-tick twice-tick twice can be heard – “ the speedlite is in the charging or overheating protection state”. It seems that the flash is not synchronized with my camera, even if my older Yongnuo YN565EX is working perfectly with the same settings of my camera.
When I’m using it in M mode the picture is good, but even if I put it to 1/1 or 1/128 I have the same output power. Both of my flashes have these issues, so I guess that I’m doing something wrong.
Any idea on how to solve the above?