If estimate lines are missing a production code, or you can't find a production code (prod. code) when linking the lines, it is usually because the prod. code has not been created in the project yet. The prod. code must first be added under Prod. codes — it will then appear in the estimate.
How to do it
Create the missing prod. codes under Prod. codes, or import them from Excel.
Go back to the estimate and link the lines to the correct prod. code.
If the estimate has already been published, publish it again once the prod. codes are in place.
Lines without a prod. code are collected under «Without prod. code», where you can link them manually.

