Indexing key & not created

INCLUDE 'AA_AFA_ERROR' OBJECT DOKU ID TX LANGUAGE E

What causes this issue?

You have entered an indexing key in the area-dependent part of the
asset master record. This indexing key is not defined. Therefore, it is
not possible to calculate the revaluation.

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?

Either create the indexing key &V1& using Customizing functions or
correct the indexing key in the asset master record.

Error message extract from SAP system. Copyright SAP SE.