Formula and average condition & can not be added.

What causes this issue?

The formula and average fee condition you are trying to add is either
already included in the fee condition list OR the formula data cannot
be determined. It is currently not possible to manually add formula
data, only to edit formula data that is determined from the condition
data.

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?

Check the F&A condition is not already included and if not then add
formula data in formula condition maintenance.

Error message extract from SAP system. Copyright SAP SE.