FAQ: MY GAMING CONTROLLER DOESN’T WORK CORRECTLY WITH STEAM'S BIG PICTURE MODE This may be due to a setting in Steam's Big Picture mode. To disable this
setting: 1- Open Steam's Big Picture and click on the Settings icon in the top right corner.
2- Go to the Controller Settings menu
3- Deselect the Generic Gamepad Configuration Support option.
Your controller should now work as expected.