Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/ad9476c69eb2a5d20f5944b7f7a8d729.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563