There are values for cost element & that are not assigned to any line ID

What causes this issue?

Not all values for the cost element are assigned to a line ID.

System Response

Let?s assume there is no assignment to a line ID for cost element K1,
then the following happens with relation to an object of the results
analysis (including the hierarchy):
If there is no posting to cost element K1, then error message KJ161 is
not issued.
If there are postings to cost element K1 and the balance relating to
this cost element is not zero, then error message KJ161 is issued.
If there are postings to cost element K1 and the balance relating to
this cost element is zero across periods, then error message KJ161 can
be issued. This depends on whether the balance formation (also across
periods) happens before or after the assignment to a line ID. This is a
decision which is only made for runtime optimization reasons. There is
information about this in individual processing under the option
?Parameter List? of the ?Logs? menu in the section ?Read Data? at the
end of the list.

How to fix this error?

Assign the corresponding cost element to a line ID. If you don't want to
include the cost element in the results analysis, assign it to a line ID
of category N.
You can access a detailed list of unassigned cost elements as follows:
Start the results analysis in individual processing mode (transaction
KKA1, KKA2, or KKA3). Select the field ?Full log?. Execute processing.
On the next screen, choose ?Logs -> Parameter List? from the menu. A
list is generated. The unassigned values are shown at the end of the
list.
If cost element "++++++++++" was shown in the message, this is because
in the assignment of costs and revenues to line IDs, you have not used a
cost element other than the full masking "++++++++++". In this case a
presummarization eliminates the information on the cost element.

Procedure for System Administrators

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

Error message extract from SAP system. Copyright SAP SE.