Thank you for reaching out to Constant Contact API Developer Support.
I’m glad to hear that you were able to resolve your issue! Also, we appreciate you sharing your resolution for other users that may run into the same type of problem.
Included below is some additional related information for visibility on the forum:
Our API documentation contains example requests in cURL for most of our endpoint requests that you can reference:
Example POST Create a Contact Request (click the tab in the example that says cURL)
Additionally, you can utilize our API Reference Page to find request body schemas & values, as well as test the functionality of our available endpoints to see how they will work once programmed within your application:
Please let us know if you have any other questions!
... View more