Diagnosis
Your project, &V1&, was not created from a standard project.
You can only assign a network to a project when it also was createdwith this standard WBS.

System Response
INCLUDE 'NA_ALLG_NOFUNKTION' OBJECT DOKU ID TX

Procedure
INCLUDE 'NA_ALLG_MOEGLICH' OBJECT DOKU ID TX
RESET N1
Using "possible entries" select a project that was created with thisstandard WBS and then select copy.
Using Create project create a new project from the standard WBS.