problem creating stompbox automations with amplitude in mainstage

Hello,

I'm trying to assign automations in order to control my amplitude effects in MainStage but It doesn't work:

It seems that I do everything allright:

• first assign the parameters in the automation window in Amplitude,
• then make MainStage learn it (or mapping it manually)

It works only for the first click either when operating with my mouse or the midi footswitch, but after amplitude stombox doesn't respond. (however the mapping is correct in the assignation panel)

I dont understand why the mapping doesn't hold, despite of the proper assignation.

any help would be so welcome, thank you