Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/8f0c9f3891715b2b3d9afae61c52ca8e.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563