With a recent update to the Shopify API system, a set of permissions has been added to each integrated app, which includes the app that needs to be installed in order to allow Linnworks to synchronize with Shopify.
In order to ensure that Linnworks is able to retrieve a list of all new open orders, mark them as shipped when the orders are processed in Linnworks, as well as update the inventory levels of all linked items, the following permissions need to be enabled in Shopify - Apps - View Private Apps - Linnworks app - Permissions:
Customer details and customer groups needs to be set to Read and write
Orders, transactions and fulfilments needs to be set to Read and write
Products, variants and collections needs to be set to Read and write