If a sales order is created with an item that has the value "Yes" in "RequireSnoToShip" field, this will be copied to the sales order (COA).
When forwarding the sales order (COA) to a shipping advice (CSA) this value will be copied.
This can be seen in the "Shipment" tab on the shipping advice item (CSAITEM).
To remove this requirement, the shipping advice (CSA) must be in status 1 or 2:
1. Go to the main level of the shipping advice (CSA)
2. Select "Activities and operations" -> "Backward ..."
3. Uncheck CSAITEM -> Shipment -> Require serial number to ship
4. Add to the picking queue and continue shipping as normal
Future orders for this product will not have this requirement as you currently changed to "No" in RequireSnoToShip