missing stylesheet

Hi – I know it isn’t a ‘pre-sale’ question, but it is a ‘pre-use’ question….

I made the purchase, downloaded the zip file and tried to install it. I was face with the message:

Unpacking the package…

Installing the theme…

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

Theme install failed.

I cannot use it as it stands, and I cannot post in the forum as it is closed for Christmas. I genuinely would like some assistance if you could spare 5 minutes, as I am really keen to get started.