Thanks everybody for the tips! I tried all of them, it is working now and I dont know exactly why. I opened the expression pedal, cleaned it a bit, reversed the polarity and then it started working, I put the polarity back to normal and it works fine now. I will dig deeper into the global settings for the expression, all I did there was to choose exp 1.
I don't k ow if it will continue working, I keep you all updated.
Thanks again so much for all the help!