New datapoint: I’m actually able to get the Space to recognize the exp pedal when I insert the jack partway in. It’s only intermittent and not a solution for the problem, but at least indicates it’s a hardware issue. The exp pedal jack is a stereo rather than the standard 1/4-inch guitar cable I was using to connect the Ernie Ball VP, so that may explain the difference, i.e. the female on the Space isn’t getting full contact with the stereo, but can get something from the mono guitar cable (when it’s in the exp jack, the volume pedal only uses a tiny fraction of its sweep to go from 0 to 100). I don’t have any contact cleaner other than alcohol swab, which I tried, but maybe I can get some and try that. Otherwise getting the jack replaced would be the answer, which kinda sucks.