Why does Shopify show a product as sold out when inventory is available?

This is usually a location or variant mismatch. Shopify uses the stock for the exact variant and the locations that can fulfill an online order; it doesn't make a product purchasable just because the admin shows inventory somewhere. Open the affected variant and check its Online Store availability, then check `Edit locations` and the available quantity at each location. Stock held at a retail-only or otherwise non-fulfilling location can still count toward your total while the storefront shows sold out. Also check that the product is active in an online-fulfilling location, plus any fulfillment app, shipping-profile, or order-routing setup that manages that variant. If the storefront is still stale after the settings are right, test the exact product URL in an incognito window and then check the theme or app that's rendering availability.