Before the Lulu xPress App can validate an order and begin production, the order must include a phone number. If a phone number is not included in the order's shipping information, the order will be marked as "Invalid" and will not proceed to production until a phone number is manually added by the merchant.You can make adding a phone number a requirement for your customers during checkout through your Shopify settings. To do this, click the Settings gear in the lower left corner, then click Checkout. Under Form Options, select Required for the option "Shipping address phone number." Lastly, click Save. Your changes will take effect immediately.