Assignment: Assign line ID & to a single valuation group

What causes this issue?

The <DS:GLOS.line_ID>line ID</> specifies information such as whether
the costs are to be treated as costs with a requirement to capitalize
or a prohibition to capitalize.
To specify how the costs are to be treated, you assign each line ID to
a key in Customizing indicating whether there is a <LS>requirement to
capitalize</>, a <LS>prohibition to capitalize</>, or an <LS>option to
capitalize</>.

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

Go into Customizing and check the assignment of the line IDs.

Error message extract from SAP system. Copyright SAP SE.