I ran the request https://secure.na1.echosign.com/public/oauth?redirect_uri=https://example.com/oauthDemo& response_type=code&client_id=B9JMDG5263XP3V&scope=user_login:self+agreement_send:account using rest client.The request is a GET.As per the Adobe Document Cloud Electronic Signature Service and Digital E-signature Solution — E-signature and Digital Signature S… doc the response is not coming.The client_id is a valid echosign account and generates a accesstoken if the rest api is used through swagger.Let me know if i am wrong some place.The request was executed through postman.
I tried your request to see where that takes in Postman and I get invalid_request.
This means that one or more of your parameters are invalid.
You should try to go to your applications and check again that the redirect URL is same as one you use in Postman for given application (or else you get invalid call), the client_id is same as in application and what kind of rights you are requesting are contained in the application.
A successful call should show in Postman the login page to your account.
PS: make sure that you don't have spaces inside the URL.