Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/bf3d1a9ffd803505e1e13ff8a59f1719.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563