Status & can only be set by the system

What causes this issue?

You can save an allocation without leaving the value assignment screen.
However, if the class contains characteristics which have the <ZH>Entry
required</> indicator, the system automatically sets the status of the
allocation to "incomplete". In classification, the system
<ZH>internally</> distinguishes between an "incomplete" status which is
set by the user and an "incomplete" status which is set by the system.

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?

Choose a status using the possible entries functions.

Error message extract from SAP system. Copyright SAP SE.