Put X-API-Key in header
In C# and various languages, the key must be placed into the header. Also, try the following statement when making a test request.
request.Headers.Add("x-api-key", "YOUR_API_KEY");
Note: Rather than adding x-api-key in the post data.
Test in Postman
Ensure that a successful connection is made is Postman. Related articles below provide a step-by-step guide.