Need advice getting a volume pedal to work

Need some advice or ideas. My controller is a Novation Launchkey 88mk3. It has only a sustain pedal input. No input for expression/volume (CV type), pedal. I thought I could solve getting a pedal going by using a Midi Solutions Pedal Controller box. It comes preprogrammed to merge CC007 volume into the midi stream which is connected to my interface via Din jack. Midi out from keyboard to midi in of control box. Pedal jack inserts into box and midi out from box to interface is supposed to merge the CC7 messages into the stream. But when I connect everything I get zero midi signal passing through the box to the interface. Not just no pedal control, no midi at all. Of course checked pedal and cables with tester and on other keyboards. Concluded box must be bad even though when I insert in in the cable tester it shows correctly the pins 2,4&5 are connected properly. So maybe circuitry in box is bad as no led light on box shows as on other MS. Products. Sweetwater sending a new in but if that doesn’t work still, does anyone have any ideas or alternatives to get a master volume pedal workin with this rig?

I would rather go for one of these little fellows:
https://www.audiofront.net/MIDIExpression.php

These are highly configurable and it would provide your pedal(s) as a separate controller device, which you could use in Gig Performer as you want or need.
You wouldn’t be bound to any CC# or channel, wouldn’t have to rely on a proper “merge” implementation or whatsoever… It should be as easy as: connect it, configure it, use it.
You can also search the forums for “audiofront” and you’ll find quite a few postings about that topic!

Same issue here, I bought a Logidy UMI3 pedal. It has the CC pedal connection you’re looking for as well as (3) footswitches that can be programmed to send any MIDI messages needed thru USB. I use one of them to advance Songlist parts live.