'Apply' button not working on controller (xbox controller on pc)

I am using an xbox one controller on PC. The 'apply' button (start button, or menu button on the one controller) is not functional/mapped. Clicking it does not work.

I was initially playing the game with controller (it detected the controller when I first loaded the game and asked if I wanted to use it and I clicked yes) and managed to get around the button not working by clicking to join a server with the mouse or letting the server host click the start button. When trying to create my own server, this was not working. I thought maybe I could create the server using keyboard and mouse, then switch back to controller, so I went into settings and changed the input to keyboard and mouse. Once I had finished setting up the server, I went back into settings to revert to controller and realised my huge error.

The apply button is required to change back to controller. And it's not functional. So now I can't change back to controller at all.

I tried remapping. I tried uninstalling and reinstalling the game to see if it would default me to controller, but this did not work and I'm stuck on keyboard controls now.

Things I have tried:

- remapping the 'start' button to something else. It seems to register the remap, as the start icon next to 'apply' is changed to whatever I select, however when I click to apply, nothing happens.

- uninstalling and reinstalling. the game loads up defaulted to keyboard controls and I cannot change this.

I don't have a 360 or other generic controller so I don't know if this is solely an issue with the xbox one controller.

Not sure it's relevant, but the xbox one controller, including the start/menu button, works fine with Don't Starve, the solo game.