Simple garage door opener

Hi,
I'm trying to create what should be the world's simplest Shelly Uni application, shorting two wires for about 1 second to trigger a garage door opener. I connect one set of the output leads of the Shelly Uni in parallel with a wall-mounted switch. The switch has 28V over it when open, and 20mA flowing through it when closed. As far as I can read the Shelly Uni specs (max 36V DC and max 100mA), this should be a perfect fit, and I assume that the outputs are actually MOSFETs despite a mention of "open collector outputs" somewhere. What I find strange if the outputs are indeed just MOSFETs, is that there is no mention of ON resistance?

Anyways, nothing happens when I press the button and (presumably) short the output leads, so I'd appreciate any advice or feedback. Is there perhaps a non-obvious trick to enable the outputs at all? Or could I simply have a defective unit? Or are the outputs actually open collector after all?

I power the Uni with 12V (Not that I see how/why that should matter, but just to come clean).

Cheers,

T. Kalunken

Thanks for the replies for so far. The button I refer to is simply the button in the Shelly app, so the circuit itself could hardly be any simpler. No external components besides the switch, which is not even part of the circuit while the Uni is being operated.

I appreciate the advice on other Shelly units, but hind-sight is always 20-20. I started researching the Shelly Plug S for something completely unrelated, and when I finally bought a few of those I also grabbed a Shelly Uni, which was on sale, seemed like a cool toy, and superficially also seemed to have the right spec. So it's not like I discarded the other Shelly options, I just happened to start with the Uni.

Assuming that the problem is just the ON resistance, I'll try using the two output in parallel. I haven't checked if it possible to tie the two outputs together in the Shelly app, but it will be an interesting test regardless of the practical use.