Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/513c1fb13b8be0d91b4d8812c953e45c.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563