This is an identified issue, but the resolution has not been well managed. My controller comes today and I still do not have a code.
You should get your activation code after getting the shipping notice and the issue they shared has been fixed now I think? You can contact support via https://support.google.com/stadia but from a lot of posts I've seen on here and Reddit, they will likely tell you it may take 3-5 business days and to contact them again if you still haven't received the code by the end of the week.
I got my "order has been shipped" notice on the 18th, but still no activation code. I've requested a call back on the support page, but haven't received a call back (even though it says it's a less than 1 minute wait time). I'm not sure where to go next.
Same here, FE arrives today, but no code in sight. I think the confusion is coming from the idea that they are sending codes out in order, and hardware... well no idea how they did that. I thought FE meant day of release access, but apparently that was changed with out notice.
Update - received my hardware & still no access code.The Stadia team support chat is disabled (though it says it's 24/7) and I've submitted for a call at least a half dozen times and not received one (it says <1 minute wait). This is shockily terrible.