Chosen Solution
It’s a bit odd that all three are not functional. I have done repairs which required complete removal of the motherboard and connected everything back together without event. There’s some more info at repair.wiki which provides a little extra insight, but not much more than you have already. I would post some pictures of what this area looks like on your board. Both the actual game cartridge reader board (the pins on the connector to the main board included) and the board itself without the cartridge reader connected. Make sure there are no bent pins or tears in the cable.
I also followed this guide just today and my touch screen and game cartridge reader isn’t working, I’m really worried I damaged something even though it looks fine and is seated fine, did you ever figure out what went wrong or what to try? :(
