I can get why the seller would be hesitant. You first mentioned you're in Canada and would drive down and pick it up but then later say you have a US address to ship it to.
I'm sure this is all 100% legit and I'm in no way saying there is anything shady going one at all on your part but, I can see how a seller might be a little weary. Some sellers have been burned in the past and are very strict is how they sell and who they sell to. Scammers tend to change up the terms they agree to and sometimes ask for items to be shipped to an address that is not theirs. They then claim they never got it.
Again, not saying this is you. Just trying to consider where the seller might be coming from?
That being said, the seller should respond in some way.