Swissonic EasyKey 49

I like this keyboard, it has none of the extra features I'd never use anyway that just takes up space, it feels solid and sturdy and most important of all, it has full size keys with a nice feel to them. However, I've tried for hours getting my sustain pedal to work with it and it just won't. The manual doesn't make sense of the issue, changing the numbers in the edit window doesn't change anything. No combination of unplugging, depressing, plugging back in etc helps.

Either the pedal is working inversed or it's not working at all. Kinda sad, I should have checked this out thoroughly when I still could return it and not just assume I could solve it later on. Oh well, it works for stuff that doesn't need sustaining I guess...