NSC | Special Work Order Assembly Error: You must enter at least one line item for this transaction

Scenario

User is encountering an error when saving the Sales Order: You must enter at least one line item for this transaction linked to an assembly.

Cause

1.) Bill of Material is currently set as Default for a different Location (e.g. Location A) when the Sales Order Location is set to a different Location (e.g. Location B).
2.) The Bill of Material is neither set as a Default for any Location nor as a Master Default.

Solution

To resolve, edit the Special Work Order Item by going to Item Record > Manufacturing tab > Bill of Materials subtab, either set the Bill of Material to include the Sales Order Location as Default for Location or set the Bill of Material as Master Default to make it available for all Locations.