So, the difference is 2 hours of desperate work.
Normally, a flat cable can have 4 different positions between 2 connectors.
The correct position is the 1st, than you can change the left side with the right side this is the 2nd, and then you can flip it, and you have again 2 different cases.
After repairing a 5d, I mounted this cable upside down, closed the camera… The result: camera was not turning on. I disassembled it 5 times. Than I’ve found this innocent flex cable. And the right position was NOT with the readable inscription 🙂 – the correct position was that on the right picture…