Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/d17f4ae3c8834331c03b8ad96e8e4df6.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563