Hello,
Compare themes/xstore-child/header.php and themes/xstore/header.php files. Add our changes to your child theme version of the header.php.
Actually, why did you copy that file to child theme? To add GA code? Use Insert header and Footers plugin to add the GA code before the close head tag and remove the header.php from the child theme if you don’t want to update that in the future.
Regards