Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/e2f8681a2d307fb492fbe7550b5e0ed3.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563