Option to ship to Canada is grayed out

I sold an item to a buyer on Amazon Canada but realized the box was damaged and it’s an expensive item, so I canceled the order. I can’t list in Used (or as this is a toy, more specifically Collectible) on Amazon Canada, so I told him to buy it from me on Amazon US, but it doesn’t show up for him and I now see, I can’t offer shipping to Canada. When I click North America, only Mexico can be checked but Canada is grayed out.

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How can this be fixed?