Error Message "missing style.css"

Guys,
Joined yesterday to the premium elite membership. Today while installing Pro Sites, I received this message:

>>

Installing Theme from uploaded file: 371697_pro-sites-3.4.7.2.zip
Unpacking the package…

Installing the theme…

The package could not be installed. The theme is missing the style.css stylesheet.

Theme install failed.

<<<

Any idea why this is happening? I don't see in the how to's this dependency.

Thanks,
Kevin