Login to your Amazon account and visit the main link to see if you are eligible.
In order to qualify for the promotional credit, you must: (1) be the recipient of the corresponding offer (either via email or on Amazon.ca); (2) purchase at least $50 in Amazon.ca Gift Cards ("GCs") in a single order at Amazon.ca between December 8, 2016, and December 22, 2016, 11:59 PM (PT); and (3) enter the promotional code "HOLIDAY16CA" in the "Gift Cards & Promotional Codes" box when you check out.
• Purchases must be for at least $50 in combined GC value, and the GCs must be purchased in a single order at Amazon.ca.
• Offer valid on GCs purchased at Amazon.ca and, in the case of Email GCs scheduled in advance, delivered before December 22, 2016.
• For qualifying purchases, a promotional code of $10 ("Promo Code") will be automatically applied to the customer account associated with the Amazon.ca account used to purchase the GCs after the qualifying order has shipped. An email notification will also be sent within three (3) days of shipping, confirming your Amazon.ca Credit.
• Promo Code is valid through and expires on February 14, 2017, 11:59 PM (PT).
• Limit one Promo Code per customer/primary email address.
• Promo Code may be applied only to eligible products sold by Amazon.ca, Inc. and its affiliates and does not apply to products sold by third-party merchants through the Amazon.ca site.
• Savings from the Promo Code will be reflected on the final checkout page on qualifying orders.
• If items purchased with the Promo Code are returned, the amount of the Promo Code used to purchase such items will be subtracted from your return credit.
• The Promo Code is non-transferable and may not be resold.
• The Promo Code may not be combined with other offers.
• If you violate any of these terms and conditions, the promotion will be invalid.
• Void where prohibited.
• Amazon reserves the right to modify or cancel the promotion at any time.
• Additional restrictions apply, see www.amazon.ca/promos for details.
So, I wasn't eligible for the offer, went on chat and the CS applied promotional credit to my account :)