Hello Aman_Mamdani,
Thank you for reaching out to Constant Contact API Developer Support. My team is here to assist outside software developers with questions about building into Constant Contact's API.
An Unauthorized error can be returned either when the access token or API key that you provided is not valid or has expired, or possibly if the request is not formatted correctly.
Could you please provide us with the API key that you are using to make the request, as the full request(s) where you are receiving the response error (including URL, headers, and request body), the full response body, as well as timeframes so that we can so that we can better assist you in identifying the root cause of the issue?
In order to communicate this information securely, please send it to us via email at webservices@constantcontact.com .
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