#325 Cannot connect to webcalendar from external network

[dmedia]

I am able to access webcalendar from internal network, everything works good. When I try to access the webcalendar from an external network I get the following error.
The following error was encountered while trying to retrieve the URL: http://directedmedia.no-ip.net/OMA-Calendar/index.php?

Unable to determine IP address from host name "xibo-server"

The DNS server returned:

Name Error: The domain name does not exist.

This means that the cache was not able to resolve the hostname presented in the URL. Check if the address is correct.

If I try to access another server on the same setup like URL: http://directedmedia.no-ip.net/demo-xibo-server/index.php?
Everything works fine.

Also I have a test.php file that report the php info on each web server and both work correctly.

I have no idea why I cannot get access to the webcalendar from an external network.
Any ideas?