New RGC RAD2X cable not working

I know contact the mfr, but I just got this new translucent black RAD2X for Mega Drive 2 model and it does nothing. It has no external power source and if there is supposed to be an indicator light I don't see one. I've tried it with both EDFX and a Retroupgrades PCE RGB, firmly connected, on an original white PC Engine and I get no HDMI signal. Both of these RGB expansion units just work with inferior/cheaper cables, so I'm at a loss what could be going on here. Was I wrong to expect this to work? The EDFX at least is listed as compatible.

This thing also requires a mini HDMI adapter, which I dislike, so that's another factor. I have exactly one such adapter in the house that was working with a Pi unit it came with as far as I know, and I have no idea what could make such a small inert object go bad anyway. I'd have to order some more just to swap out as I don't really use these for anything else, but maybe that is the culprit?