1/ Have you cleared all cache?
2/ 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 the cache of the browser, and check then. Maybe one of the additional plugins is a reason for problems.
3/ What do you mean by “the child theme stopped working”? Please describe problem in more detail.
One standard license is valid only for 1 project. Running multiple projects on a single license is a copyright violation.