With Black Ops DLC you need to download the DLC for the region of the game. So for example if you have a US disc, you'll need to download with a US account.
Also remember that they can tell where you are in the world via your IP address, so it is possible that it is blocking you from downloading because you have a Canadian IP but an account from another region.
Did this solve your problem?
Sorry this didn't help.
Great! Thanks for marking this as the answer.
How satisfied are you with this reply?
Thanks for your feedback, it helps us improve the site.