Not able to get access token

[JKYog]

I follow these steps to get access token using post man. for v3 

1. Loginto https://app.constantcontact.com/pages/dma/portal/
2. create app and generate secretcode
3. make below request through browser after changing client_id
https://api.cc.email/v3/idfed?client_id=7391d41d-15f8-4767-a8e5-a43d1fa5f1bb&redirect_uri=https://lo...

4. Enable f12 for browser debug mode it will show the url in debug mode
something like https://localhost?code=Btm-DfwTesRXTplmOCEGpBI6CTD_GTL1FPclEAEt

5. Open PostMan and select request type as Post and make the below request after changing the Basic Auth and code parameter
Basic <client_id>:<secret_key>(base64encode)
https://idfed.constantcontact.com/as/token.oauth2?code=GfqUoci56ZQF7jV9tFXVslgXRJjUzLDsYVPBcgDJ&redi...

Im getting this json error message.

{
"error_description": "unable to parse Authorization header javax.security.auth.login.LoginException: HTTP Basic username has invalid content com.pingidentity.common.security.InvalidInputException: Value for parameter \"Authorization\" is invalid. Value doesn't match regular expression: .*",
"error": "invalid_client"
}

[Courtney_E]

Thank you for reaching out to Constant Contact API Developer Support. My team is here to assist outside software developers with questions 

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