The selection is not possible

What causes this issue?

You have entered too many selection criteria.
On the initial screen, you may only fill in either <LS>Purchase
order</>, <LS>Delivery note</> or <LS>GR document</>.
In the multiple selection screen, you may only fill in per line one of
the fields <LS>Purchase order</>, <LS>Delivery note</> or
<LS>GR document</>.

How to fix this error?

What you should do depends on whether the purchase order and the
delivery note or GR document belong together.
Example:
Purchase order,,Goods receipt with delivery note
450000012,,ABC
450000025,,XYZ

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

If purchase order number 450000012 and delivery note number ABC are
specified on the invoice, you have to enter either the purchase order
number or the delivery note number.
If you enter the purchase order number, later on the selection screen
you will receive a list of all goods receipts.
If you enter the delivery note number, later on the selection screen
you will only receive a list of the items delivered.
(In multiple selection if you enter both purchase order and delivery
note number in more than one line, the system will ask you to delete
one line.)
If purchase order number 450000012 and delivery note number XYZ are both
on the invoice, in multiple selection you have to enter the PO number in
one line and the delivery note number in the next.
On the selection screen you receive a list of all goods receipts for
PO number 450000012 and all items for delivery note XYZ.

Error message extract from SAP system. Copyright SAP SE.