I was under the impression it was a used gun, but I suppose it could have been new?Importer would have guessed the same as the FFL, only difference is the importer is the responsible party for the firearm once it arrives here.
Unless gun is a used gun when the FFL received it, the FFL couldn't test fire it. It wouldn't be new anymore and he would have to sell it as used and profit go bye bye. Sadly, FFLs aren't like car dealers where they can drive the car around a bit and then still sell as "new" with some miles on it.
While CAI would be responsible for the gun as soon as FFL transferred ownership, the FFL might have been willing to help. In this case, though, it doesn't seem like the FFL was really willing to do anything so it might be a moot point at this time.
Anyways, if it was new, shame on the manufacturer for not test firing it and sending proof of that with the gun. Still, FFL should at a minimum give the buyer $150 store credit, if not full refund.