Hello John,
I got same error when I tried to install Yelp importer. My facebook importer is working just fine. I used Client ID instead of the App ID and API Key instead of App secret, just like what you did, and I got same error.
This made me read more the Yelp Agreement of Service to use the Yelp API, I found out that we, the GeoDirectory plugin users or others, work indirectly to propmote Yelp products on our websites. So, I decided to not go further with Yelp importer and Facebook importer would be just fine for me.
Please correct me if I’m wrong in this understanding.