Purchase order item & & does not exist

What causes this issue?

There is no item with the specified number in the purchase order.

How to fix this error?

Check your input and correct it if necessary. If your input was correct,
the invoice contains an error. To find the right PO and item number, you
can generate a list of all purchase orders for the supplier or for the
materials specified in the invoice by positioning the cursor on the
field <LS>Purchase order</> and pressing F4.

Error message extract from SAP system. Copyright SAP SE.