I'm trying to generate an access\_token using DocuSign API using code (<https://developers.docusign.com/platform/auth/authcode/authcode-get-token>)

I'm calling POST request to: <https://account-d.docusign.com/oauth/token>

with the following body (application/x-www-form-urlencoded):
{
"grant\_type": "authorization\_code",
"code": "code that I got after login with the user"
}

Authorization: "Basic encodedBase64(integrationKey:SecretKey)"

The error I'm getting is:
{
"error": "invalid\_grant",
"error\_description": "unauthorized\_client"
}

I really need help here. Thanks so much