Activate projects in controlling area &1 in &2

What causes this issue?

You have assigned to a WBS element or a network, although the "Project"
indicator has not been set in controlling area &V1& in fiscal year &V2&.

System Response

As the "Project" indicator has not been set, you cannot execute a check
or a consistent data update in Controlling. The WBS element or network
you have entered can be used as a true account assignment object, but
will not be updated. If you also post to a cost center, this will only
be debited statistically.

How to fix this error?

If the limitations detailed under system activities do not present a
problem for you, you can ignore this error message.
To do this, see the Implementation Guide (IMG) "Controlling General"
under workstep <DS:SIMG.SIMG_CFMENUORK3OBA5>"Change Message Control"</>
(message class "KI", message number "141").
If you are using the fields "WBS element" or "Network" to archive your
own information for a posting in the SAP system, you should make use of
the enhancement to the account assignment block, which offers you
user-defined fields.
See the IMG "Special Ledger" under <DS:SIMG.SIMG_XXAK_OXK3>"Maintain
account assignment block"</>.

Error message extract from SAP system. Copyright SAP SE.