I have tried printing a shipping label and am seeing one of following errors returned:
Package sequence number 0 contains 0 items. Must provide content
Package 0 has no allocated order item(s).
This error appears if you have no items in an order package or in the order itself. Please ensure that you have at least one item in the order. If there is only a service item added instead of a SKU, this error will be shown as well.
If you have split the order into multiple packages, then you will need to check Linnworks.net > Order > Open Orders > right-click on an order > Shipping > Split Packaging screen and make sure all the items are assigned into packages correctly.
Shipping - Packaging Groups
Open Orders: How to Split Packaging