Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/a377b7d86d028a18e00025c3af29a4bd.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563