I am not at all sure about this, having only built V5 kits from stock parts, but looking at the picture from the V5 build instructions:
It looks like the Zynthian kit uses what MECCANIXITY calls a type B cable and you have gotten a type A. From your link:
Two Kind of Types - A and B
“A Type” flat cable means — the contacting side of the 2 top pin is on the same side(Both towards to up or down).
“B Type” flat cable means — the contacting side of the 2 top pin is on the opposite side(One towards to up, the other towards to down).
So the result is the pins are reversed left to right from what they should be,