How to generate access token when using sso instead of oauth2.

My company uses sso integration with humanity, so I don't have a username or password. I was given an app id and app secret, but no matter what I do I get the below error following the authentication guide.

{"error":"invalid_client","error_description":"The client credentials are invalid"}

Is there another url or grant type required for generating a token when using sso instead of oauth2?