Make sure that your server is assigned a static IP address. The problem is a bit more than it seems on the front, and is because the Microsoft .NET Framework on which your identity sync appliance is based doesn't recognize your proxy settings.
Open the following file:
Add the following text to the end of the file:
<system.net> <defaultProxy> <proxy usesystemdefault="true" proxyaddress="http://<PROXYIP>:80" bypassonlocal="true" /> </defaultProxy> </system.net>
In this text, the placeholder
<PROXYIP> represents the actual proxy IP address and this IP address is the static IP address of your server.