Language selector only show up in the theme editor
If you have created multiple languages for your Shopify store, you may experience an issue where the selector only show up in the theme editor, but not in the actual store. This issue happens when you create multiple domain, but forgot to enable the languages for each domain.
To fix this issue, open your Shopify admin, click on "Online store" and "Domains":
Then, for each of your managed domain, click on "Manage":
Then make sure to select the languages you want to show for the specific domain (the screenshot below is an example, the list of languages will be different based on the languages you have created):