automation sustain groove agent se 5

Hello ,
I am looking for an automated sustain of a percussion in groove agent se5,

the other automation works correctly, but the 3rd small square in the window of the curve, does not react when I record the automation, this curve is located in the EDIT> AMP tab

can you give me the procedure to follow to carry out this operation …
a big thank-you

nobody helped me ??

there is really no one to help me

pls help me!