Advice on matrix config

Hi all, I’ve hit a wall with this one unfortunately. Got these from Ali and really struggling to get them going with WLED. No matter what I try, only the first string works. I have two of these and they both show the same behaviour (both tested and work as they should before cutting the cable). Also tried with 3 different controllers and still get the same.

Another buyer made a comment which I can’t fully under (see screenshot).

Any recommendations on what to try?