Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/2d9564de60fe9f41e7dd3c8f3cc7f99e.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563