Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/d81e266d9e66b6dc29ac924d8499e7c0.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563