Valid If - default system error

[Mike_T]

I’m using a QR code scanner. When I set the valid if formula to:
(IN([_THIS], QR Codes[QR_Code]))
and I scan a QR code that is valid and On the list, it works fine. When I scan a code NOT on the list I get the default system error “The scan result didn’t match any known entries”.

When I add a NOT(…) around the above formula the results are reversed and the error message is the one I input into the invalid value error field.

How do I get my custom error message to appear in the correct scenario above?