Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/9edf37f6d2e8a0f76d7af8c376526b91.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563