This characteristic is not appropriate as a partitioning characteristic

What causes this issue?

For the field name for partitioning, you must enter a selected
characteristic used in the segment table and not hidden for CO-PA. The
field you entered/selected is not an active characteristic in the
segment table.

How to fix this error?

Enter a characteristic from the section "Characteristics in the segment
table" as the field name for partitioning.
Note: You can choose one of these characteristics by double-clicking
it.

How to fix this error?

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.