The rewards widget is not appearing on the storefront

The widget renders for signed-out visitors too, showing a sign-in prompt instead of a balance, so "nothing at all on the page" is almost never a customer problem. Check, in order:

1. The app embed is off. Go to Online Store, Themes, Customize, App embeds, and confirm the Miko Loyalty widget is switched on.
2. You enabled it on a different theme. App embeds belong to one theme. Duplicating a theme, installing a new one, or switching which theme is published does not carry the embed across. Re-check the embed after any theme change.
3. You are looking at a preview. Confirm you are viewing the published theme, not a preview link of another one.