Did the agents scan your boarding pass at any point? Do you have a copy of them? I believe it should say Sky Club on it if you are allowed access. As others have indicated, FC flights to Canada should qualify as an international Skyteam premium cabin flight. Although they've split up the sections, the language on the website really hasn't changed. Here's what it used to say (snapshot from March 2017).

Delta One or SkyTeam Premium Cabin Passenger

Customers traveling in Delta One on an international Delta flight or a domestic Delta flight connecting to/from a same-day international Delta flight* in Delta One or travel in international First/Business Class on a SkyTeam-operated flight. (In order to qualify for Club access, the customer must be confirmed in the premium (first or business class) cabin for the international segment of their itinerary.)

*International Travel includes: Customers traveling to/from Europe, Asia, South America, Central America, Africa, Canada and Mexico (excludes travel to/from the Caribbean, Guam, Palau and Saipan).