Purchase order & has deletion indicator &

What causes this issue?

The <GL:purchase_order>purchase order</> you entered has been deleted,
is flagged for deletion, or is blocked. It therefore cannot be
processed.

System Response

INCLUDE MB_NA_T160M

How to fix this error?

INCLUDE NA_EINGABE_PRUEFEN
INCLUDE MB_NA_BESTELLUNG_SUCHEN

Error message extract from SAP system. Copyright SAP SE.