Purchase order & does not exist

What causes this issue?

You have entered a <DS:GLOS.3526C0CEAFAB52B9E10000009B38F974>purchase
order number</> that does not exist in the system.

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
INCLUDE MB_NA_BESTELLUNG_SUCHEN

Error message extract from SAP system. Copyright SAP SE.