Servo output disabled

Good day all

Im trying trying to setup my APM in my glider. I have 2 aileron servos on separate channels( so that i can do crow braking and have stabilization on both ailerons) . When I go to servo output to assign channel 5 to my second aileron, that blocks are grey and I cant do anything to assign input 5 to aileron and there is no servo option under parameters . Can somebody please help as to how I can assign it.

What FW version are you using. Please update your mission Planner version.

I am using the latest mission planner , with firmware version 3.4.0 on my APM ( as that is the last firmware available for the APM).
I have tried using older versions of mission planner , but still no success

have you been able to solve the issue??

No not yet. Have tried to solve it , but couldnt figure it out