You may find that your systems are marking orders as shipped before tracking is added. In this scenario, the webhook will only fire once and it will not retrieve the tracking information as there is none set against the order. This will result in the tracking not being sent to the marketplace.
To relieve this, we can setup a time lag that is bespoke to your business. The setting allows us to wait ample time to capture tracking. Please liaise with our support staff to work out the best lag time to wait and enable the setting.