upgrade 6.1 to 7.04

[Lorcan O'Neill]

I'm trying to upgrade from 6.10 to 7.04 but I get the following error

Authentication failed

Authenticating the upgrade failed. There may be a problem with the network
or with the server.

The update manager states

" Setting Preferences

The Update Manager
      Preferences button displays the Software
        Preferences dialog. From this dialog you can perform the
      following tasks:
"

   There seems to be no Preferences button in Update Manager. Can someone
explain/help?
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