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You'll know the upgrade is over when the following message "upgrade complete. Please check your front - office theme is functional (try to make an order, check theme)" appears in green, along with the following final log entry: "End of process".
The upgrader also indicates that you should re-enable your shop, but before you do that, you should first check that everything is working in your back - office: no errors, all products and categories are in place with their images and attached files, etc. Until you have checked that everything is okay in your shop, it is better to keep it from the public eye.
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Once you have made sure your PrestaShop installation is up and running, you can re-enable your shop using the option in the "Maintenance" page of the "Preferences" menu, then make tests on your front - office: browse products, sort them, try to order one, etc. In short, go through the entire buying process in order to make sure that you won't miss a sale.
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