#4869 Problem Upgrading

[stuartxt]

My client has moved their web server behind a firewall, since then I have not been able to do a Webmin upgrade. It will not work from "Latest version from www.webmin.com" or from an uploaded file.

I get the following when trying the on-line method:
No package signature verification done.
Failed to upgrade from www.webmin.com : Not a valid Webmin Debian package file

And from an uploaded file (webmin_1.831_all.deb):
No package signature verification done.
Failed to upgrade from uploaded file : Not a valid Webmin Debian package file

What do I need to look at to get this to work again ?