Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/d8ad2c81bd0d38ed73529e7e7849c2ca.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563