CommentStreams:B8e4804cfb6fe30388d1cdf6326480b6

OK, sorry, I figured it out. I was trying to follow the schematic from the 4-pin LED momentary push button, but everything works as expected if you follow what the Wiki suggests.

The LED button has four pins: S1, S2, LED+, LED- The x728 has four pins: PWR, GND, GND, LED+

Connect them as such: PWR - S1 GND - S2 GND - LED- LED+ - LED+

I don't know why my incorrect wiring ever worked, but this is what it always should have been. Leaving this here in case anyone else has the same problem!