Hello,
In this case, your custom changes in child theme can be the reason for the problem. Try the next, activate parent theme, re-name child theme via FTP, then upload XStore child theme that can be downloaded from this page – https://www.8theme.com/downloads , activate this child theme and check the result. If there is no the problem, you need to take a closer look at what changes were done in the first child theme.
If the problem persists even with the new child theme, provide us with FTP access, and we will take a closer look (after the weekend).
In the text of the notice, that you previously provided, facebook-for-woocommerce plugin was mentioned. Temporarily disable that plugin also.
Regards