Just wondering, whats yours shipped?
You should get your activation code after getting the shipping notice. From a lot of posts I've seen on here and Reddit, Stadia support are saying it may take 3-5 business days and to contact them if you still haven't received the code by the end of the week.
I ordered the Founders Edition in June and I have received my package but still no code. I love how Stadia turned off customer support yesterday....I requested a call 5 times today already!