OAuth2 flow redirect to AdobeSign homepage

As a user if I am already authenticated to the AdobeSign UI, I can't authorize a third-party application using OAuth2.

Currently:

Step 1 - My App do not already have my access token

Step 2 - I call https://secure.echosign.com/public/oauth?redirect_uri=https://myapp.com/callback&response_type=code&client_id=[MY_CLIENT]&scope=agreement_send:self+agreement_read:self+user_read:self
Step 3 - I am redirected to AdobeSign Homepage

What I am expecting:

Step 1 - My App do not already have my accessToken

Step 3- I am redirected to the "consent screen" where I can validate the scopes

Step 4 - I am redirected to My App with my access code as a parameter

Step 5 - My app retrieve my access token

The workaround:

Step 1 - flush my browser cookies

Step 2- do "What I am expecting:"

What is going on?

Thank you, Hugo