Grouping WBS element & not processed since valuated stock + CO version 0

What causes this issue?

You want to process a WBS element with valuated stock with the CO
version 0. However, CO version 0 is only valid for unvaluated stock.

System Response

The trasnaction cannot be executed.

How to fix this error?

Choose a CO version not equal to 0.

Error message extract from SAP system. Copyright SAP SE.