Hi Yorgos, Mike
The pedal in and outs on the back of the Basestation Pro are designed to emulate an audio source, so that you can use any volume pedal, within reason, with them. It actually sounds as if Yorgos is doing the right thing, and there may be another problem, although Mike is quite correct, you do need to calibrate the pedals as most pedals vary wildly in their endpoints. Yorgos, could you give Aaron a call in customer services on Tuesday? He'll try to help you get this working. For your information, there have been a couple of reports of a software problem with the current Testing releases and pedals as well so it's quite possibly something out of your control, ie; our fault...
John