Pipelines API endpoint returns "Resource not found"

I am able to get to the point of retrieving an access token so that when I make an API call to /api/2.0/repositories/

{username}/{repo_slug} I get data returned; i.e. my credentials are correct and API is working up to that point.

However, as soon as add "pipelines" to the endpoint I get "Resource not found errors"; /api/2.0/repositories/{username}

/

{repo_slug}

/pipelines/. A attempted the same endpoint as a POST request with data to run a custom build process defined in my bitbucket-pipelines.yml

Currently I have no idea how to continue to debug this.