Hello,
You use 4.28.1 theme version, so you need to have 1.0.23 version of Core plugin. Please download the required plugin version from our site – https://www.8theme.com/download-plugins/ then delete current XStore Core plugin on your site and upload 1.0.23 version of the plugin. Also, you need to activate Massive Addons for WPBakery Page Builder plugin.
Read more – https://xstore.helpscoutdocs.com/article/36-included-plugins
Regards