Has Harry had any treatment at all from your vet?
If not, there are no records to see and I would get someone else to ring breeder’s vet to say that as he had his first vaccinations with them, can he have the booster too? Like Min, we are registered with two vets, the first a local one we can walk to and another that offers 24 hour care which the local vet can’t. I also took Maisie to a third vet to have her keyhole spay as neither of the first two vets did it.