If your site is behind a firewall, for example during testing, you will need to configure your firewall to allow ChannelUnity to call into it.
ChannelUnity requires that the shopping cart site you connect into is publicly accessible.
Although ChannelUnity internally runs on many servers, we have minimal public IP addresses.
To allow ChannelUnity to access your site you should whitelist the IP addresses:
89.238.143.187
89.238.143.186