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Go to Appearance > Themes > install and activate Storefront theme, deactivate XStore core plugin. Check how the delivery calculation works on Cart with the Storefront theme. Do you still have the mentioned issue with the Storefront theme? Record a video or make screenshots. Enable XStore theme and Core plugin again after testing. Let us know about the results.
One standard license is valid only for 1 project. Running multiple projects on a single license is a copyright violation.