I too have the Morley Volume Plus Pro Series but cannot get it to work correctly (it's plugged into EXT 2). At first, the position was reversed even after I changed the setting to "Invert", but somehow that's fixed now.
Currently, even when I have the heel down, the Position monitor will kick up to about 40% after a few seconds, even after I manually turn down the Position to 0%. And when I'm using the pedal, putting weight on the heel will add more sound than just leaving it heel down. It seems very glitchy, and I have never had issue with the pedal before connecting it to HX Effects. Activating the volume switch has not helped, as it did for @chacharlafuzz. But maybe I'm missing something.