Web Gateway, could not establish trust relationship SSL/TLS channel

1st attempt at installing Web Gateway and its failing with the error:

 the underlying connection was closed: could not establish trust relationship for the SSL/TLS secure channel.

Please check your internet connection.

 

the machine is a patched windows 7 pro, on AD domain.

the app.exe is run locally as admin.  no issues with network connectivity.

 

 

Any ideas what is causing this error.