Hi Ndiab,
Really can't help with that, that error is returned by DocuSign. Your use case is also a bit different from what is implemented in the demo, in our demo you generate one document and only then you send to DocuSign to sign.
Did you confirm if the App created did the registration successfully go to your DocuSign profile :
https://account-d.docusign.com/me/appconsent
You should see the app that you created previous listed:

You can set the REST APIs log level to full and see what information is exchanged and confirm with DocuSign the expected behaviour.
It seems that either you are not using the latest version of the components, or not configuring the components correctly.
Make sure you go to https://<Your environment>/DocusignConfigurator/ and generated public and private keys and follow the detailed instructions there and you go to Service Center inside DocuSign2_1APIs and DocuSignReactiveDemo modules and you configure the site properties accordingly.