Square Business child theme (S5) not installed ??

i installed 8.7 beta and activated it

then i tried to install the following child theme, Square Business (S5):

https://dp1.wlthemes.com/?skin=dt_five

but this failed, or kinda sorta:

the child them directory contained content but here is the full installation message:

#### BEGIN MESSAGE #### (this line not included in message)

Installing Theme: Child Theme 1

Downloading install package from https://www.premiumpress.com/_childthemes/download.php?key=dt_five…

Unpacking the package…

Installing the theme…

This theme requires a parent theme. Checking if it is installed…

Preparing to install Child Theme 1…

Downloading install package from https://www.premiumpress.com/_childthemes/download.php?key=%5BXXX%5D…

Unpacking the package…

Installing the theme…

The package could not be installed. The theme contains no files.

Theme install failed.

Successfully installed the theme Child Theme 1.

Return to Theme Installer

#### END MESSAGE #### (this line not included in message)

so, i’m not sure what up

when i clicked to see the Details of that child theme (Square Business), firefox presented a “This Connection is Untrusted” warning and included the following message:

dp1.wlthemes.com uses an invalid security certificate.
The certificate is not trusted because it is self-signed.
The certificate is only valid for server.markfail.com
(Error code: sec_error_unknown_issuer)

so, it looks like content was installed but not activated but somehow not complete??

anyone got any ideas? i’d love to use the Square Business child theme

thanks