Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/5bc7f8c1f34394a9239f5d81d7aedb99.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563