Hello, @moacirsilva
Please make sure that the theme has “xstore” name + Core plugin (et-core-plugin) wasn’t renamed also.
If you use 6.1.5 version of the XStore the Core should be 1.4.5 version.
+ min required PHP version is 7.0 https://xstore.helpscoutdocs.com/article/60-xstore-theme-requirements
Regards