Everything was powered from the 24v, and the power to the RPi is good. It’s possible that a trace is cut somewhere, though the board had been working and I haven’t moved or remounted it.
I turned on station 1 (on the RPi) and checked the voltage on corresponding pin of the 74HC595N, thinking that I might find 5v there. But there wasn’t any voltage there. Not sure where else to look as I’m really not equipped to do detailed debugging of the board, so I guess my only real option is to buy a new one.