Box Sign API Genrating 404 Error, Developer Account

I am creating a custom application and would like to integrate Box Sign as part of the application. At the moment, I have a box developer account with two users. I used one user to create the application (in the developer console), and another user will be used to test Box Sign API. I don't have any issues creating folders or uploading files using the API, but whenever I try to access the Box Sign Endpoint (https://api.box.com/2.0/sign_requests), it returns a 404 "not found" error. This link [ https://developer.box.com/guides/box-sign/ ] explains that the Box Sign API is only available for the following account types: Business, Business Plus, Enterprise, Enterprise Suites, and Enterprise Plus.  This may explain why I am getting the 404 error, as I do not have a paid box account, only a developer account. Can someone confirm if the developer account can access the Box Sign Endpoint? I thought the developer account would allow me to complete my development work without restriction before purchasing a paid version, but I may be wrong. Is this something I would have to reach out to support to enable?