TL;DR: I think I might be encountering two separate issues… a faulty switch chip and a bad clock signal.
I got my Jumperless kit yesterday and assembled it without issue. I checked it under a magnifying glass and didn’t see any stray solder or bridges. I flashed the latest firmware and made a sample Wokwi project, just connecting a couple rows. The LEDs lit up to show the connections, but the actual connections weren’t being made (no continuity when checked with a multimeter). I cleared the netlist and checked each row against power and ground. Row 32 showed a steady -8.68V, and row 34 showed a flakey -3.1V (both connected to switch chip E). I looked through the schematics and PCB layout and didn’t see anything that could short to cause that, so I lifted switch chip E pin 35 to disconnect row 32, figuring I could still use it and just avoid that row. I plugged the board back in and tried again, but still no luck making connections. The power, ground, and reset for each switch chip checked out fine. Checking clock and data with an oscilloscope revealed that the data net was fine, but clock net was not working properly. Rise time was good but fall time was extremely slow, so I don’t think the switch chips were actually seeing clock pulses. Thinking that something else might be weird with switch chip E, I lifted its clock pin as well, but the behavior was still the same. It’s like the RP2040 isn’t actually driving the clock signal low.
Any suggestions for other things to check? I’m currently out of ideas