[SOLVED] ArduinoHttpClient: Getting status code -3 for Post with headers

I'm using the following code (taken from example ArduinoHttpClient/PostWithHeaders.ino at master · arduino-libraries/ArduinoHttpClient · GitHub):

    httpClient.beginRequest();
    httpClient.post("/");
    httpClient.sendHeader("Content-Type", "application/x-www-form-urlencoded");
    httpClient.sendHeader("Content-Length", postData.length());
    httpClient.sendHeader("MyCustomHeader", CustomString);
    httpClient.beginBody();
    httpClient.print(postData);
    httpClient.endRequest();

A similar post request succeeds in Postman, but in the Arduino sketch I'm getting status code -3 (timeout).

I'm using the WiFiSSLClient in WiFiNINA library.

I finally got it working the following code:

    httpClient.beginRequest();
    httpClient.post(endPointURL);
    httpClient.sendHeader("Content-Type", "application/x-www-form-urlencoded");
    httpClient.sendHeader("Content-Length", 0);
    httpClient.sendHeader("MyCustomHeader", CustomString);
    httpClient.endRequest();

The endPointURL is the url path for the endpoint or resource.
Also, I removed the "https://" at the start of the host/server name the WiFiNINA SSL client connects to.