The airline should be enforcing that passengers have the QR code, even if it is not checked on arrival.
You must complete an online Passenger Locator Form (PLF)at least 24 hours before your arrival in Greece. Failure to do so in advance may result in your carrier not allowing you to travel, a 500 Euro fine on arrival or the Greek authorities not allowing you to enter the country.
I don't think you have much comeback, but potentially it depends on how garbled your name was on the form?
One question: did you try resubmitting the form at the airport? I heard from a friend they submitted the form on the app at the check-in desk and got the QR code immediately, and wondered if they were just lucky or if it is immediate?
I traveled to Greece early July and was quite impressed with the whole setup. I've been seeing quite a few last minute offers, so was considering returning.