Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/8021d7959844b6de9395ab5f7c9d3e4e.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563