Hello! I just saw your PM but thought I'd reply here to help others maybe in the future.
I think the Arp stuff is V-Trig meaning that you will need to set the IMP machine to positive pulse, from the top of my head you should leave the DOWN and DVAL around the centre or at the default values, and the UP and UVAL quite high, you might also need to ensure the volume is as high as possible and try accents too. If it does not work with these settings on the trig in, try the gate in. You could also try turning DOWN and DVAL all the way down.
Good luck, and reply back in this thread to let us know how you get on