Would guess it's starting directly at 29.11.2019, but just to be sure it might be worth checking the app constantly.
Unfortunately I believe that everyone who doesn't have access by then will miss the sale, because Grace was writing "Please note that you must be subscribed to Stadia Pro in order to access the deals, and you must be accessing the store through the mobile app. " If you don't have the code, it's logical that you can't access or buy games.
My delivery isn't expected until 26th November.
So judging by people who ordered 6th June who have no code, safe to say I'll probably miss the black Friday sale ![]()
Shame.