Fob Lock/Unlock Button Issue After Remote Start Install

Hello! First post, and this forum has been an amazing help so far.

I've installed a push button start + remote start system in my 2005 Mitsubishi Outlander.
Everything works as intended except for the lock/unlock on the FOB.
Either button I press only locks the car.

This is the kit I have (pretty much the standard random Chinese one):
https://www.amazon.ca/gp/product/B07RRXDVST/

This kit wants a negative trigger input for the door locks, which is what my car has.

I've wired it according to this chart, which matches others I've seen around the internet (wiring for 2003-2006 is all the same):
https://www.the12volt.com/installbay/forum_posts.asp?tid=44189

I'm using T-taps for the time being before I solder anything permanently.
I tapped into the wires coming directly out of the ETACS ECU.

A couple things that may have caused a hiccup:
I bought my car used from an auction. It came with a factory FOB that never worked.
I tried replacing the fob and reprogramming it to the car, but that didn't work.
When installing this new system, I simply unplugged the stock(?) system that came with the car. It looks like a similar non-descript box.
Is it possible that the old box had some relays etc installed that changed the unlock to a positive trigger?
If that were the case, I assume my current setup wouldn't work at all, even to lock it.

Tomorrow I might try to take apart the bundle from the old system to see if something was added into the wiring that might be affecting mine.

Full disclaimer: I have very little knowledge about cars, but I dabble in some home electronic projects, so I'm mostly just following tutorials here.

what happens when you use a TEST light / multi meter to see if you have the correct lock/unlock wire?