Hybrid mode footswitch D does not work

I want to use the Hybrid mode.It really works, but it is impossible to assign an affect to the D footswitch.However it works with the A B and C footswitches.
My Hybrid mode is : Presets on the lowest footswitches and effects on the highest footswitches.Can sommebody help me? I guess i have to look at the Hybrid mode settings, but i don’t know how …Thanks