Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/5267c2d4852bfb7b2d0f96e7cc51674d.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563