Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/bd44a5bbe1cf6a03c277b9dd092fd9f5.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563