Why is the Preorder button not showing on my product page? (Essent Preorder Back in Stock app)

The Preorder button replaces your theme's Add to cart button only when four things are true: the app embed is on, the campaign is Live, the product is in the campaign, and the product's stock matches the campaign's Show preorder button rule. These are the usual causes.

Check these in order

1. App embed is on. Online Store → Themes → Customize → App embeds → turn on Essential Preorder → Save. The embed is per theme, so turn it on again after you switch or publish a new theme.
2. Campaign is Live and has the product. Open the campaign and check Status, scheduling says Live (not Draft, and a Scheduled start date has passed). Then open the Preorder products tab and confirm the product and the right variants are listed.
3. Stock matches the rule. With When product is out of stock, the button shows only when the variant's stock is 0 or less. A variant with even 1 unit keeps Add to cart. If you want preorders regardless of stock, choose Always.
4. "Continue selling when out of stock" is set the right way. It must be on for Always and When product is out of stock, and off for When product is in stock. The Preorder products tab shows a banner if any product is set the wrong way, with a button to fix them all at once.
5. The placement is on. Under Preorder → Settings → General settings → Manage → Show preorder button on, check Product pages (and any other places you expect the button).
6. Stock comes from the right locations. Only locations that fulfil online orders count. See Check location fulfilment settings.
7. The product is Active and available on the Online Store sales channel.
8. Clear the cache. Check the live store in an incognito window, not the theme editor preview.

Still not showing?

Another app (product options, bundles, volume discounts) or a custom theme may be replacing the Add to cart button. Contact support with the product URL and the campaign name. We fix theme compatibility for free with collaborator access.

Full guide: Preorder button not showing: the full checklist.