Cannot install Jetpack

I downloaded Jetpack today and uploaded it on a working www.remarpro.com website hosted by an ISP. When I tried to install Jetpack installation failed and this message displayed.

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

I just searched but cannot find anything directly on this so will appreciate your help. I did find some postings where people said this forum is not to place to resolve issues with third-party vendors, and I understand that, but Jetpack comes from WordPress itself.

Hoping for help,

Alan