2399 triple splashback delay

I’m stumped. My build seems to be working, except none of the signal LEDs light up beyond a very (very) faint flicker. Is there any single component that would make all four not light up? I tried switching out one transistor thinking maybe I’d fried them all somehow, but no difference. When I try to measure the voltage coming to the LEDs, it’s just around 1v whereas the on/off LED is seeing around 2v (and working).