Purchase order & does not contain item &

What causes this issue?

In purchase order &V1&, the specified item &V2& cannot be found.

System Response

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

How to fix this error?

INCLUDE NA_EINGABE_PRUEFEN
If required, remove the item entry so that the system displays all
items of the purchase order on the selection list. Then select the
desired item(s) from the selection list.

Error message extract from SAP system. Copyright SAP SE.