3DS with no working buttons

Hi, I have a 3DS console that powers on more or less normally, but the ABXY buttons, analog stick, D-pad, shoulder buttons, and touch screen are not working.

When powered on the console boots and I see the home screen with the rotating icons on the top screen. If I press the power button the shut down screen comes on and I can either press the power button again to shut down or press the home button to go back to the main menu. The home button does work for this.

If I insert a game it shows up on the home screen. When I flip the WiFi switch on or off I can see "enabled", "disabled", or "Streetpass" in the upper left part of the top screen, so the console does seem to be running normally. It's just that none of the buttons seem to work.

There's also no sound. I don't know if the problem is related or not.

I swapped in a different motherboard into the housing and it worked fine so I know the touch screen and speakers are good.

When I take the problematic motherboard and disconnect everything except bottom + top screens, touch screen, and speakers I still can't use any buttons or the touch screen even if I press hard on the little pads on the board directly with my finger.

None of the liquid indicators are active and I'm pretty sure nobody has even opened the console before I got it. Is this something I can fix? Or should I just replace the motherboard?