Wow....this is a super rare problem to have, but it might help someone. I accidentally set my app's API key to the key for a different app of mine, which resulted in the "redirect_uri is not whitelisted" error message. I spent a couple hours pulling my hair out trying to figure out why I couldn't log in to my app anymore.
If all else fails, double check that the client_id in your callback url matches with your API key!
|an hour ago|