Yesterday I took a pedal off my pedalboard and used it on it's own w/ a 9V power supply. It worked as expected, but then today the signal doesn't seem to go through the pedal. It won't go through when it's on or off, with a power supply or a brand new 9V battery. I've check that all cords, etc. are functional... WTF?

Any ideas?

I put it back on the pedal board w/ it's built in power supply and it's fine again!