Blank Sheet Name field

I just installed this module and set up the Google side of things. On my webform page though, I can select my Doc Name, but when I try to select my Sheet Name, the dropdown is empty and none of the sheet names are displayed. I also get an error "Invalid response code from Google Docs API" but can't figure out what could be going on.

Are there specific Scopes that need to be enabled? I've got the non-sensitive Drive API scopes added, but maybe I'm missing something else?

Thanks