There are some common themes in some of these reviews that should be addressed in this searchable place.
If the pedal is not working at all, check to make sure you are using a TRS cable, and NOT a regular guitar cable. If the end has one black ring around it, that is a regular guitar/instrument cable. If it has two rings, it has two channels = stereo = TRS.
Another issue is the pedal's range when used as an expression pedal. So assuming you're using a TRS cable, you might notice the full 0-127 gets used up mostly in the middle 1/3rd of the pedal's range. That has to do with the pedal's polarity, and unfortunately this pedal doesn't have a switch or a second jack to change between TRS and RTS. I was calibrating my Airstep to use the expression pedal, and when I had it set to use RTS, I saw the range that some reviewers have seen. Then I switched it to TRS polarity, and I saw 0-127 smoothly across the entire pedal's range.
(Other than that, this little pedal is rock solid and a welcome addition to my rig.)