If it’s an obscure error in GP, rest assured that Steve Endow will find it.
Dynamics GP Land: eConnect Error 110 when Updating Existing SOP Order: Item number/location code does not exist in inventory
Sales, Purchasing & InventoryDevelopment & Integration
Archived post from 2016. Dynamics GP and the links it points to have changed since; check current documentation before relying on version-specific steps.