Cannot single sign on in Private IP

Hi, my website cannot have single sign on (SSO). I have system check and it show "Received empty response from Moodle". I have read the documentation and I am sure I have set the URL correctly.

I am wonder it may be causes by private IP in the school. i have tried to input the private IP address in the "Xmlrpc - Joomdle" plugin as well. But it is still not work.

Please help...as the site is in production already...

Thank you in advance.

There are a couple of reasons why you may get such an error. But to start what versions of Joomla and Moodle are you running?

I am using Moodle 2.1 and Joomdle 0.6 and Joomla 1.5.23

Thank you.

Just to be sure, have you enabled the xml-rpc protocol in Moodle?

Plugins/Webservices/Manage Protocols

Yes, I have enabled it.

This message usually indicates Joomla cannot connect with Moodle, so check that there are no restrictions to access Moodle URL from Joomla site.

Also check that you enabled web services on Moodle.

Yes, i have checked. Actually, I have several sites using Joomdle and all of them are working fine except this one which using private IP. That's why I think the issue is related to private IP.

Thank you so much....please help.

I don't really understand what you mean by "private ip".

Is the moodle server accesible from the internet? If not, you cannot connect an outside joomla with a moodle on a intranet.