WBS element & has activities. Delete activities first

What causes this issue?

You can only delete the dates in a WBS element if there aren't any
activities assigned to the WBS element anymore.

System Response

INCLUDE 'NA_ALLG_NOFUNCTION' OBJECT DOKU ID TX

How to fix this error?

You have the following options in deleting the dates in the WBS elements

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.