OAuth "invalid_scope" Error

At my company’s upcoming user conference we are hosting a “HackZone” where I plan to showcase an integration of our application with SmartThings using the REST API.

I am working on automating as much of the OAuth process is possible but I am getting the following error:
{
“error”: “invalid_scope”,
“error_description”: “Request for access token scope outside of authorization code scope.”
}

I setup the Oauth pieces correctly as I have done in the past. I have an OAuth Client Display Link setup in the SmartApp that points to my application that will automate the next few steps of getting the Code, Auth Token and Enpoint URL. Unfortunately I am getting the error above.

In my query to get the Auth Token, I have tried passing scope=app and also tried without it but I am still getting errors. Any ideas?