To ensure that you as a brand are informed in time before an order is rejected due to "Variant is Out of stock," you need to subscribe to Notifications in the Printlabs Dashboard. Only then will you automatically receive a notification as soon as an item goes out of stock or the inventory is low.
Good to know: Without an active subscription to the dashboard notifications, you will not receive proactive warnings — inventory and availability will then need to be checked manually in the dashboard.