You selected some activities which are in header-assigned networks

What causes this issue?

You have selected activities for the maintenance of the settlement rule
which are in a network with header account assignment.
Before you can maintain the settlement rule for all the activities you
have selected, you must first maintain the settlement rule for the
activities with header account assignment.

System Response

The system ignores your selections and first displays the header screen
of the networks with header account assignment. Then the system displays
the activity detail screens.

How to fix this error?

First maintain the settlement rule for the networks with header account
assignment and then maintain the settlement rule for the activities
with activity account assignment.

Error message extract from SAP system. Copyright SAP SE.