403

I'm getting "Access denied - insufficient permission" when trying to update a file that I am a co-owner on (I am a co-owner on the entire directory), and I am able to edit the file manually. I can successfully start the program (getting the message "Authenticated successfully! Accessing Box root folder: All Files") and download & read from files, but I get the 403 when trying to update, even though the app has read and write permissions.