Left thumb stick physically not clicking

Hi, I am asking about an issue with a used elite controller I just picked up, that is for repair. I am new to this, and was unable to figure this out myself. The left thumb stick does not click in and does not produce a response for the L3 button when pushed down. I have dissasembled it and nothing else seems to be wrong with the controller besides it not being able to click down. The stick and plastic on the inside of the joystick seems to be intact but I could not find any differences between a working joystick and this one, hence I do not know what parts to get or how to proceed. Thanks!