I just bought Fall Guys and I thought it would work out of the box with the controller I recently bought but alas, it didn’t.  I had to change a few settings to get it working.

How to: Fix controller not working on Steam

1. Make sure you disconnect your controller
2. Open Steam
3. Open Steam’s Big Picture mode

4. Click the Library

5. Find and select Fall Guys: Ultimate Knockout

6. Click Manage Game

7. Go to Controller Options

8. Change the setting Steam input per game setting to Forced On

9. Restart Steam
10. And Voila!  It should pickup the controller the next time you run it.