I believe it is because in the hidden analogue mode, the cables behave in a different way than standard documentation. You can see another example for another intercom here:
Basically red and black are bus+ and bus- for ring, and blue and purple are bus+ and bus- for opening.
I think that “Comparator invert” option was the last peace to the puzzle I will email Nuki to get this enabled and update the forum once I’ve tried it out
If you already emailed Nuki to enable the hidden analog mode, you can just access this menu yourself, as described in the previous post.
It sounds to me like maybe you didn’t enable hidden analog mode from step 1 which is why this might not be working.