Ckfinder + watermark plugin, problem, watermark plugin gives an error, how to solve the problem?

Question

PHP

Hello, the second day I'm trying to solve the problem with the watermark plugin for Ckfinder.
I installed the plugin in Ckfinder in the config.php file and inserted this.

include_once "plugins/watermark/Watermark.php";

$config['ImageWatermark'] = [  
  'imagePath' => __DIR__ . 'plugins/watermark/waterznak.png',             
    'position' => [
        'right'  => 'center',
        'bottom' => 'center'
    ]                         
];

I climb into the editor on the site, then I go to Ckfinder, where there is a photo selection and upload, it gives such an error.
System error:
Unable to read server XML response, empty string received.
Screenshot:

Who faced such a problem? tell me how to solve it, maybe there is another plugin for Ckfinder.
You need a plugin that will put a watermark on the photo when uploading via Ckfinder.