I double-checked all connections and didn't notice any mistakes. I was able to program the SLG46826V, but it was not functioning. It gets no power. I removed the regulator, tested it, and it worked. Then I noticed the regulator was not connected to the power rail on the far left side, which powers the SLG46826V module. I was so focused on looking for short circuits that I missed it, I guess.

Now I've implemented the function that reads from the SLG46826V and determines which key is pressed. I need to do some more testing, but based on initial testing of the keypad, it seems to work without issues.

The keypad matrix scanning is almost complete! :)