java.net.SocketTimeoutException in JAVA okhttp client and AWS server php script

Question

I want to send a formbody using okhttp in java from the Android APP client-side to check if new file is available on the server, and handle this request through a PHP script on AWS EC2 server to send the URL to the new file back to APP.

Client side code:

    @RequiresApi(api = Build.VERSION_CODES.KITKAT)
    static ResponseBody requestUpdate(Long name){
        Log.d(TAG, "requestUpdate: method starts");
        OkHttpClient client = new OkHttpClient.Builder()
                .connectTimeout(60, TimeUnit.SECONDS)
                .readTimeout(60,TimeUnit.SECONDS)
                .writeTimeout(60,TimeUnit.SECONDS)
                .build();

        String fileName = Long.toString(name);
        RequestBody formBody = new FormBody.Builder()
                .add("name", fileName)
                .build();
        Request request = new Request.Builder()
                .url("https://url_to_aws_ec2_server/handleRequest.php")
                .post(formBody)
                .build();

        try (Response response = client.newCall(request).execute()) {
            Log.d(TAG, "requestUpdate: execute success");
            if (!response.isSuccessful()) throw new IOException("Unexpected code " + response);
            System.out.println(response.body().string());
            return response.body();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }

Server side code:

<?php
    header("Content-Type: application/json"); 

    $fileClient = pathinfo($_POST['name'], PATHINFO_FILENAME);
    $filedir = "./uploads/";

    // acquire the lastest file on server
    if(is_dir($filedir))
        {
            $fl=scandir($filedir);
            foreach($fl as $value){
                if($value !="." && $value!=".." && pathinfo($value, PATHINFO_EXTENSION) == "mp4"){
                    if(strcmp($value, $fileServer)>0){
                        $fileServer = $value;
                    }    
                }
            }
            // compare it with the one from client side
            if (strcmp($fileClient, $fileServer)>=0){
                $response['success'] = TRUE;
                $response['flag'] = 0;
            }else{
                $response['success'] = TRUE; 
                $response['flag'] = 1;
                $response['link'] = sprintf("http://url_to_ec2_server/%s", $fileServer);
            }
        }
        else{
            $response['success'] = FALSE;
            echo("Your directory does not exist.");
        }

    echo json_encode($response);
?>

The error I got:

2020-08-25 15:01:28.574 2523-2579/com.example.ses_adplatform_test W/System.err: 
java.net.SocketTimeoutException: 
failed to connect to url_to_aws_ec2_server/13.59.157.98 (port 443) from /10.0.2.16 (port 54238) after 60000ms

What I have tried

1. I have changed timeout duration to 2 minutes in OkHttpClient builder - it still throws errors
2. I have made sure that the php script does work by navigating to it directly - I got the expected response in the browser
3. I have added inbound and outbound rules for HTTPS on AWS ec2 instance
4. I have tried and change the timeout duration to 5 minutes but my APP crashed due to "runtime abort" somehow.

My questions are:

1. Is there anything to do with my server on this specific issue? Am I supposed to set up my server for okhttp client in some way?
2. Is there anything else I could try to solve this problem? Or any possible reason you guys think that can cause it?

Thank you!!