9 months is a pretty long time for someone to still consider giving you an exchange or refund.

Personally if i had had to get one exchanged then I would have bolted in the replacement and given it a god through the range to check it was working, and if i hadn't, after 9 months i wouldn't have expected the seller to be interested in my call even if it was genuine as , like has been said, i could have been using the box for all they know.