Hello,
Thanks for using our theme.
The latest version of XStore (8.0.10v) you can find on ThemeForest. To download the theme from ThemeForest you need to enter the downloads area ThemeForest account, where you can view all your purchased themes. Find the XStore template among them, and click on the Download button to the right of the main content. Download the theme’s .zip file directly.
XStore Core plugin can be downloaded from this page – https://www.8theme.com/downloads/
https://xstore.helpscoutdocs.com/article/37-plugins-update
About PCLZIP_ERR_BAD_FORMAT (-10), try the solution from this topic – https://www.8theme.com/topic/the-package-could-not-be-installed-pclzip_err_bad_format-10-unable-to-find-2/#post-273465
or do the update via FTP – https://xstore.helpscoutdocs.com/article/63-theme-update
Regards