If you are receiving this error (Unable to Add Shipment Tracking Entity. Error:{"code":"rest_no_route","message":"No route was found matching the URL and request method.","data":{"status":404}}), it means there is no Tracking URL added to the courier service. To resolve this please do the following:
Click Shipping Management then Couriers.
Find the Courier then ManageCourierServices.
Click Edit and add a Tracking URL.
If you have errors within the Import Errors screen, please do the following:
Click Connect then Import Errors.
Tick the Errors.
Select Resync Connect Action from the Bulk Actions.
Click Go.