Some customers are experiencing issues with migrating to the new Amazon Shipping integration. Please double-check that all steps have been followed as per this guide: https://help.linnworks.com/support/solutions/articles/7000073357
If the migration is successful but your orders are returning errors, please make sure that the following guidelines have been followed: https://docs.linnworks.com/articles/#!documentation/amazon-shipping-rules
In case nothing from the above works, please raise a ticket with Linnworks Support.