I hate having to say this, but that NUX Tape Core Pedal has failed me and I'm sending it back. It worked fine for a couple of days but position *5 no longer produced an echo and that's the main one for me.
Looking on the forums there is clearly a software issue with these and it is such a shame because it's a great sounding pedal.
Maybe they will solve it, but until they do it's of no use to me.