Scope doesn't seem to work for Amazon Music

I'm trying to get an access token for use with the Amazon Music API, and following the documentation here: https://developer.amazon.com/docs/music/API_browse_LWA.html#calling-lwa-for-use-with-amazon-music it states that I need to pass through a scope of "amazon_music:access". However, when I do this I get back the following response.

{
    "error_description": "The request has an invalid parameter : scope",
    "error": "invalid_scope"
}

EDIT: I forgot to mention that our account manager has assured us we do have access to the Amazon Music API after spending a few months going through the process of getting access.

question