The listen button is not appearing on the storefront

Two separate things gate it, and it is worth checking them in this order:

1. Your plan. The listen feature is available on the Growth and Pro plans. On other plans the button does not become active, even though the block can still be placed in the theme.
2. The theme block. It is a theme app block, so it renders only on the template it was added to, only on the published theme, and it does not carry across when a theme is duplicated or replaced. Re-add it after any theme change.

The feature reads text aloud using the browser's own speech engine rather than generating audio files, so nothing needs to be uploaded or hosted, and available voices differ between browsers and devices.