Price index for pool & & & & not maintained

What causes this issue?

Price index not found for the specified pool; index valuation cannot be
carried out.

How to fix this error?

Choose the function "Maintain layer --> Change". Enter the specified
pool on the initial screen and branch to the layer overview. Place the
cursor on the current fiscal year and branch to the details screen for
the layer. On this screen, enter data in the field "Price index", then
save your entries.

Error message extract from SAP system. Copyright SAP SE.