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.