Sales scheduling agreement item &1 missing in APO

<LS>&CAUSE&</>
Sales scheduling agreement item &V1& is missing in SAP APO.

How to fix this error?

You have the following options:
<ZH>Send sales scheduling agreement item &V1& to SAP APO:</>

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

If you are planning the sales scheduling agreement item &V1& using
<LS>Delivery Schedule Processing for the Sales Scheduling Agreement</>
in SAP APO, first select sales scheduling agreement item &V1& and then
execute the <LS>Send to APO</> function.
This sends sales scheduling agreement item &V1& to SAP APO.
<ZH>Remove sales scheduling agreement item &V1& from the active
integration model in SAP R/3:</>
If you are planning sales scheduling agreement item &V1& in SAP R/3,
remove the <LS>sales scheduling agreement</> object for
material/location combination &V2&/&V3& in SAP R/3 from the active
integration model.

Error message extract from SAP system. Copyright SAP SE.