Problems sending JSON by POST when compiled

Question

I am with an application whose one of the modules is responsible for sending a JSON to an online API that synchronizes the data with a back system. When this module is run or debugged into an IDE, it performs this task successfully, but when run on the application installed on Windows (.jar) it does not work and returns a 500 API error, I have already contacted her developer and he cannot make the log available to me because it is an Handler. I considered the possibility of being either permissions or some firewall block since the IDE works and the application doesn’t, so I disabled everything and continued with the same problem. The javax.net library is used, including in another module that makes a request similar to less data flow, it communicates with the API correctly.

Follows the excerpt of the code in which the shipment is made:

URL url = new URL(urlPost);
HttpsURLConnection con = (HttpsURLConnection) url.openConnection();

    UploadRetaguardaModel upload = new UploadRetaguardaModel();
    upload.montarJsonPrincipal();
    JSONObject main = upload.mainObject;
    upload.closeConnection();

try {

    //add request header
    con.setRequestMethod("POST");
    con.setRequestProperty("User-Agent", USER_AGENT);
    con.setRequestProperty("Accept-Language", "en-US,en;q=0.5");
    con.setRequestProperty("Accept-charset", "UTF-8");
    con.setRequestProperty("Content-Type", "application/json");
    con.setDoOutput(true);

    // Send post request
    OutputStream os = con.getOutputStream();
    os.write(main.toString().getBytes());
    os.close();

    int responseCode = con.getResponseCode();

    BufferedReader in = new BufferedReader(new InputStreamReader(con.getInputStream()));
    String inputLine;
    StringBuffer response = new StringBuffer();

    while ((inputLine = in.readLine()) != null) {
        response.append(inputLine);
    }
    in.close();
    [...]
}

Error returning in stacktrace:

java.io.IOException: Server returned HTTP response code: 500 for URL: [...]
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
    at sun.net.www.protocol.http.HttpURLConnection$10.run(HttpURLConnection.java:1926)
    at sun.net.www.protocol.http.HttpURLConnection$10.run(HttpURLConnection.java:1921)
    at java.security.AccessController.doPrivileged(Native Method)
    at sun.net.www.protocol.http.HttpURLConnection.getChainedException(HttpURLConnection.java:1920)
    at sun.net.www.protocol.http.HttpURLConnection.getInputStream0(HttpURLConnection.java:1490)
    at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1474)
    at sun.net.www.protocol.https.HttpsURLConnectionImpl.getInputStream(HttpsURLConnectionImpl.java:254)

Updating: This chunk of code worked correctly on Linux Mint, Windows 10 and 7 (on which they were tested) remains this error.