Major problem with my GP premium license implementation

Hi,
After much essays and errors with Wordpress themes, I became totally convinced of GeneratePress usefulness, and did thus purchase a premium license in January 2016. Got a license key, downloaded the gp-premium.zip file, but didn't create an account.

Now, after a recent hostile hacking of my hosted Wordpress, and as the site still was in its infancy, I just wiped all of it.

Problem is that after I installed anew a Wordpress (4.5), the gp-premium.zip file I downloaded last January doesn't work anymore: Wordpress returns an error message stating that "the theme has no style.ccs file" (accurate French to English translation here).

As concurrently the GP "Updates" option* in the Wordpress admin panel, that was the advertised other way to validate the GP license key, has manifestly disappeared, I'm at a complete loss as how to implement my GP premium license on this new Wordpress install.

Thanks in advance for the solution,

FridRick

*Note:
"1. Go to "Appearance > GeneratePress".
2. Enter your license key into the "Updates" box.
3. Click the "Update" button next to the field where you added your license key."