Android: Uploading image file and form data via post request always fails

Question

I am using BasicImageDownloader to download the image from facebook-graph (I can confirm for a fact that the URL works and the file is downloaded) and then using Retrofit to make HTTP post request in which I attach the image file and some form data. It always fails and does not hit my API in the backend with the request. Here is my code snippet. Any suggestion will be appreciated. (I have changed the value of the baseURL to "www.example.com" but if required I can supply it.)

dependency:

implementation 'com.squareup.retrofit2:retrofit:2.5.0'
implementation 'com.squareup.retrofit2:converter-gson:2.5.0'
implementation 'com.squareup.okhttp3:okhttp:3.12.0'
implementation 'com.google.code.gson:gson:2.8.5'

API interface class

package com.redhen.cuttiin.customerInterface;

import com.teckdk.cuttiin.model.LoggedIn;
import java.util.Map;
import okhttp3.MultipartBody;
import okhttp3.RequestBody;
import okhttp3.ResponseBody;
import retrofit2.Call;
import retrofit2.http.Body;
import retrofit2.http.Header;
import retrofit2.http.Multipart;
import retrofit2.http.POST;
import retrofit2.http.Part;
import retrofit2.http.PartMap;
import retrofit2.http.Url;

public interface CustomerApi {
   @Multipart
   @POST("/api/customer/signup")
   Call<ResponseBody> createUser(@Part MultipartBody.Part part,@PartMap 
   Map<String, RequestBody> params);
}

Where I make the HTTP post request method

    private void createCustomer(final String email, final String firstName, final String lastName, final String url) {
    Retrofit retrofit = new Retrofit.Builder()
            .baseUrl("https://teckdkdev.online/")
            .addConverterFactory(GsonConverterFactory.create())
            .build();

    CustomerApi customerApi = retrofit.create(CustomerApi.class);



    Calendar calendar = Calendar.getInstance();
    SimpleDateFormat mdformat = new SimpleDateFormat("YYYY-MM-DD HH:mm:ss", Locale.US);
    final String strDate = mdformat.format(calendar.getTime());
    final String imageName = UUID.randomUUID().toString();


    BasicImageDownloader basicImageDownloader = new BasicImageDownloader(new BasicImageDownloader.OnImageLoaderListener() {
        @Override
        public void onError(BasicImageDownloader.ImageError error) {
            Log.i("ERROR", "Error code " + error.getErrorCode());

        }

        @Override
        public void onProgressChange(int percent) {

        }

        @Override
        public void onComplete(Bitmap result) {
            final Bitmap.CompressFormat mFormat = Bitmap.CompressFormat.JPEG;
            final File myImageFile = new File(Environment.getExternalStorageDirectory().getAbsolutePath() +
                    File.separator + "image_test" + File.separator + imageName + "." + mFormat.name().toLowerCase());

            HashMap<String, RequestBody> params = new HashMap<>();
            params.put("firstName", toRequestBody(firstName));
            params.put("lastName", toRequestBody(lastName));
            params.put("email", toRequestBody(email));
            params.put("profileImageName", toRequestBody(imageName));
            params.put("password", toRequestBody("not available"));
            params.put("dateCreated", toRequestBody(strDate));
            params.put("dateCreatedTimezone", toRequestBody(userTimezone));
            params.put("dateCreatedCalendar", toRequestBody(userCalendar));
            params.put("dateCreatedLocale", toRequestBody(userLocale));
            params.put("authenticationType", toRequestBody("facebook"));
            params.put("role", toRequestBody("customer"));
            params.put("barberShopOwner", toRequestBody("NO"));
            params.put("accountDeactivated", toRequestBody("NO"));

            RequestBody requestBody = RequestBody.create(MediaType.parse("multipart/form-data"), myImageFile);
            MultipartBody.Part part = MultipartBody.Part.createFormData("file", myImageFile.getName(), requestBody);

            Retrofit retrofit = new Retrofit.Builder()
                    .baseUrl("https://example.com/")
                    .build();

            CustomerApi customerApi = retrofit.create(CustomerApi.class);
            customerApi.createUser(part, params).enqueue(new Callback<ResponseBody>() {
                @Override
                public void onResponse(Call<ResponseBody> call, retrofit2.Response<ResponseBody> response) {
                    try {

                        Log.d("response data", "message" + response.body().string());
                        System.out.println(response);
                    }catch (Exception e) {
                        e.printStackTrace();
                        System.out.println(response);
                    }

                }

                @Override
                public void onFailure(Call<ResponseBody> call, Throwable t) {
                    Log.i("error occured", "something died");
                    System.out.println(call.request().toString());

                }
            });
        }
    });

    basicImageDownloader.download(url, true);
}

public RequestBody toRequestBody(String value) {
    RequestBody body = RequestBody.create(MediaType.parse("text/plain"), value);
    return body;
}

I came about doing this way using this Question asked and this Question asked