1/ Try to disable all the third-party plugins (including cache plugins), that do not come bundled with XStore https://xstore.helpscoutdocs.com/article/36-included-plugins , clear cache of browser, and check how it works then.
2/ Enable debug mode in WordPress – https://wordpress.org/support/article/debugging-in-wordpress/ to find out what error appears on your site, it will point you in the right direction what needs to be fixed.
3/ If this doesn’t help, provide temporary wp-admin and FTP access, so we can take a closer look.
