Does not server meet theme requirements https://xstore.helpscoutdocs.com/article/60-xstore-theme-requirements ?
It will be difficult for you to work with the site without FTP.
We can tell you nothing and can’t offer any solution if we don’t see server error logs. Could you provide us with server error logs at least?
One standard license is valid only for 1 project. Running multiple projects on a single license is a copyright violation.