This notice comes from Subscriptio plugin that can’t be activated using the purchise code of XStore theme. Please, read article about bundled plugins https://help.market.envato.com/hc/en-us/articles/213762463-Bundled-Plugins
“Some plugins may ask for a purchase code for registration/activation once installed, however, you can simply ignore these messages as bundled plugins do not require activation or registration. ” https://xstore.helpscoutdocs.com/category/9-plugins
Also, don’t keep plugins enabled if you don’t use its functionality. Every additional plugin slows down your site a little bit because it calls additional styles and scripts.
