Ummm...let me get this straight
- "A" lens
- Aperture LOCKED at A setting
- Green button does nothing in Av or M
The expected behavior is this:
In Av: Nothing should happen when you press the green button, but exposure should be OK.
In M: Again, the green button does nothing, correct exposure depends on adjusting shutterspeed/f-stop until the viewfinder display indicates correct exposure.
To rule out issues with the aperture stop-down, take the lens off the camera and rotate the aperture ring manually. The iris should change with each click stop. Check both extremes small/large. At the smallest aperture, make sure that flicking the actuator lever opens/closes the iris with no sticking.
There are more extensive tests you can do with the lens on the camera to confirm proper stop-down, but the instructions would be very long and I am short of time!
Steve