Can't send JSON in a Java HTTP POST request

I'm getting a 'Server returned HTTP response code: 500' error although I have checked what I'm sending (I even tried sending it with an online tool and it worked). The API Key and the JSON are correct. I get this error when trying to read the input stream with 'connection.getInputStream()'. Where could this be comming frome ? Did I forget something ? I am trying to implement this feature from the openrouteservice API : https://openrouteservice.org/dev/#/api-docs/v2/directions/{profile}/post

 public static UPSRoute getRoute(Location start, Location end, String language) { if (language.equals("fr")) { JSONObject jsonObject = null; try { URL url = new URL("https://api.openrouteservice.org/v2/directions/foot-walking"); String payload = "{\"coordinates\":[[" + start.getCoordinates() + "],[" + end.getCoordinates() + "]],\"language\":\"fr\"}"; System.out.println(payload); //{"coordinates":[[1.463478,43.562038],[1.471717,43.560787]],"language":"fr"} byte[] postData = payload.getBytes(StandardCharsets.UTF_8); HttpURLConnection connection = (HttpURLConnection)url.openConnection(); connection.setRequestMethod("POST"); connection.setRequestProperty("Authorization", API_KEY); connection.setRequestProperty("Accept", "application/json, application/geo+json, application/gpx+xml, img/png; charset=utf-8"); connection.setDoOutput(true); try (DataOutputStream wr = new DataOutputStream(connection.getOutputStream())) { wr.write(postData); } BufferedReader in = new BufferedReader(new InputStreamReader(connection.getInputStream())); // Error is right here String inputLine; StringBuffer content = new StringBuffer(); while ((inputLine = in.readLine()) != null) { content.append(inputLine); } in.close(); connection.disconnect(); jsonObject = new JSONObject(content.toString()); } catch (IOException | JSONException e) { e.printStackTrace(); } return new UPSRoute(jsonObject); } else { return getRoute(start, end); } } 

Here is the error :

java.io.IOException: Server returned HTTP response code: 500 for URL: https://api.openrouteservice.org/v2/directions/foot-walking/json at java.base/sun.net.www.protocol.http.HttpURLConnection.getInputStream0(HttpURLConnection.java:1913) at java.base/sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1509) at java.base/sun.net.www.protocol.https.HttpsURLConnectionImpl.getInputStream(HttpsURLConnectionImpl.java:245) at UPSRouteService.getRoute(UPSRouteService.java:63) at Main.main(Main.java:5)