To connect to Simplifi you need the User API Key as well as your Application API Key.
How to generate the User API Key
Click on your User
Click in the Menu to left on "Api Key"
Generate an User API Key
Application API Key
The Application API Key is provided by the Simplifi Client Success Rep team. Note that this is not the Public key of an account within the Simplifi UI. We are referring to the Application Key. Expect a 36 character string.
Contact your Simplifi Client Success Rep for more details.