Pixel/Conversion Tracking is off.

Typically, conversion pixels are triggered on the Thank You page. However, if you have post-purchase offers on your store, customers may not reach the Thank You page.

For example, if a customer is presented with a post-purchase offer but then closes the tab without being redirected to the Thank You page.

In such cases, using a traditional setup, it might appear as if the order never converted due to the customer never making it to the Thank You page. To avoid this, it is best to configure your store's tracking pixels to fire the purchase event on the Post Purchase Page, and then optionally fire it again on the Thank You page if no Post Purchase offer was viewed.

For more information, please refer to Shopify's documentation on Post Purchase Pixel Tracking.