As a fellow user of XStore, I find that the theme requires a lot of resources to function correctly on the onset. Typically I will import the demo to a local installation of WordPress on my computer, since it has much more resources than a website server. Then once the demo is successfully installed, I will export the site using either Local By Flywheel or WP All-In-One Migration and import it to the host’s installation of WordPress. I hope this helps to some degree
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