Storage in Nougat

Question

I have written the following code to store the taken image photo. But for some reason, it works in all Android OS in United States but it does not work in Nougat Bulgaria. I do not have access to Bulgaria, but my app user saying that they cannot able to store the image.

Post.java

@Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        switch (requestCode) {
            case PermissionUtil.MY_PERMISSIONS_REQUEST_WRITE_EXTERNAL_STORAGE:
                if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                    switch (ImageUtil.userSelectionID) {
                        case R.id.selectPhotoProduct:
                            ImageUtil.showFileChooser(this);
                            break;
                        case R.id.takePhotoProduct:
                            if(PermissionUtil.checkPhotoPermission(this) ) {
                                ImageUtil.buildPicturePickerIntent(this.getPackageManager(), this);
                            }
                            break;
                        default:
                            break;
                    }
                }
                else {
                    // Deny code!! A message can be given.
                }
                break;
            case PermissionUtil.MY_PERMISSIONS_REQUEST_CAMERA:
                if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                    switch (ImageUtil.userSelectionID) {
                        case R.id.selectPhotoProduct:
                            if(PermissionUtil.checkStoragePermission(this)) {
                                ImageUtil.showFileChooser(this);
                            }
                            break;
                        case R.id.takePhotoProduct:
                            if(PermissionUtil.checkStoragePermission(this)) {
                                ImageUtil.buildPicturePickerIntent(this.getPackageManager(), this);
                            }
                            break;
                        default:
                            break;
                    }
                }
                else {
                    // Deny code!! A message can be given.
                }
                break;
            default:
                break;
        }
    }

PermissionUtil.java

 @TargetApi(Build.VERSION_CODES.JELLY_BEAN)
 public static boolean checkStoragePermission(final Context context)
 {
        int currentAPIVersion = Build.VERSION.SDK_INT;
        if(currentAPIVersion>=android.os.Build.VERSION_CODES.M)
        {
            if (ContextCompat.checkSelfPermission(context, Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED) {
                if (ActivityCompat.shouldShowRequestPermissionRationale((Activity) context, android.Manifest.permission.WRITE_EXTERNAL_STORAGE)) {
                    AlertDialog.Builder alertBuilder = new AlertDialog.Builder(context);
                    alertBuilder.setCancelable(true);
                    alertBuilder.setTitle(context.getString(R.string.permission_necessary));
                    alertBuilder.setMessage(context.getString(R.string.camera_permission_necessary));
                    alertBuilder.setPositiveButton(android.R.string.yes, new DialogInterface.OnClickListener() {
                        @TargetApi(Build.VERSION_CODES.JELLY_BEAN)
                        public void onClick(DialogInterface dialog, int which) {
                            ActivityCompat.requestPermissions((Activity) context, new String[]{android.Manifest.permission.WRITE_EXTERNAL_STORAGE}, MY_PERMISSIONS_REQUEST_WRITE_EXTERNAL_STORAGE);
                        }
                    });
                    AlertDialog alert = alertBuilder.create();
                    alert.show();
                } else {
                    ActivityCompat.requestPermissions((Activity) context, new String[]{android.Manifest.permission.WRITE_EXTERNAL_STORAGE}, MY_PERMISSIONS_REQUEST_WRITE_EXTERNAL_STORAGE);
                }
                return false;
            } else {
                return true;
            }
        } else {
            return true;
        }
}