Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/8d2039b34a5a1ca035f2a3cbedc8596c.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563