No (suitable) item found for purchase order &

What causes this issue?

The purchase order you entered does not contain any items that can be
invoiced. This can have one of the following causes:
No invoice receipt is defined for the purchase order items.
GR-based Invoice Verification has been defined for the purchase order
items but no goods that can be invoiced have been received.
The purchase order is for a service for which no entry or acceptance of
services performed has been made.

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

If you entered an invalid purchase order number, please correct the
entry.
If the purchase order number is valid, you may wish to switch to
preliminary posting to initially park the document without reference to
the purchase order. You can then post the document once the goods have
been received or the services performed have been entered.

Error message extract from SAP system. Copyright SAP SE.