Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/7bd941580a4e8f248feb6e5c1e90d37b.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563