What did you do before noticed the problem (installed an additional plugin, make changes in files)?
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 then. Maybe one of the additional plugins is a reason for the problem.
If this is not the fault of plugins, provide temporary wp-admin and FTP access, we will check it more deeply.
