Functional area is not possible for account assignment category &1

What causes this issue?

It is only possible to choose a functional area for account assignment
categories with 'sales order' ('E') as an consumption posting
indicator.

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?

Choose a reliable account assignment category, or delete the functional
area.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.