Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/c2b7cd00a8feba1a9f4f50942b944618.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563