Chosen Solution

So I was carrying my controller up the stairs because I was moving the location of my gamecube in my house. On my way up, I dropped the controller and it fell down the stairs and hit the ground. Since then, the A button on the gamecube controller does not work at all. I already tried cleaning it. I think there is an issue with the sensor. PLEASE help me, if you can. Thanks!

@alban92 time to take it apart and to take a really close look at it. Use these guides to work on the controller and use this guide Adding images to an existing question to post some good images so we can see what you see.