1. Use the store owner account to enter the Shopify admin center, click "Products", and select the product that is out of stock.

2. Click "All locations" and switch to JetPrint Fullfillment.

3. Click the check box and click "Bulk edit."

4. You will then enter the inventory management page. There are two options in the table: "Continue selling when out of stock" and "Track quantity" You only need to check the options except "Track quantity" As shown in the image below.

5. Finally, click "Save" and enter your online store to check whether this product can be purchased normally.