can’t install child. Error message No valid plugins

I installed the Astra child theme on one of my blogs from the https://wpastra.com/child-theme-generator/

it worked fine on first blog, but couldn’t do it on the other one.

Installing Plugin from uploaded file: astra-child.zip
Unpacking the package…
Installing the plugin…
The package could not be installed. No valid plugins were found.
Plugin installation failed.

Kept downloading it, simple and extra options. Tried multiple times. nothing ever got installed, got the same error message each time.