… I cant make it work to control the wah sweep. I assign the manual control to the expression pedal, it sweeps from zero to max but the sound is still auto-wah …
Sounds like you might have some influence from the secondary modulations: Depth Mod / Speed Mod / Mod Rate / Mod Source. Try something like this, neutralizing the parameters in the 2nd row:

I set the Q-Intensity, Bottom & Depth to median values. Adjust those up or down to taste.
Shape to Manual, Manual Mod mapped to the expression pedal or expression via MIDI CC.