Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/6cc9e877ca92e54a8480a897e8f8898f.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563