Hello MatthewV573,
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.
When making the request for the Authorization Code, after granting access, you will be redirected to a blank page and the code can be found within the blank page's URL, and/or can be retrieved if you have chosen to customize your redirect URL.
If you continue to run into issue with this, please reach out to our team directly/securely via email at webservices@constantcontact.com with the API key that you are using, and the URL returned for the blank screen (if available in the program you are using) so that we can take a look at our logs and assist further.
Please have a look and let us know if you have any other questions!
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