Hello,
Can’t tell you the reason without server error logs. So, your hosting provider should check the server error logs and report us if you have any errors related to the theme or XStore plugin there. Because at this moment fatal error is related to WooCommerce and we can do nothing with this from our side.
Next time don’t skip the main plugins update for so long. Because as you can see it caused the issues.
And we would recommend testing updates on the staging site next time before updating the production site.
Waiting for the reply from your hosting provider.
Regards