@Frankii My guess is that there are currently hundreds of users calling support right now to ask about the status of their order/activation code, so they might get overwhelmed and can't keep up. There's no guaranteed date when you'll be getting the code, but it is known that Google is currently pushing codes as fast as the can.
You can check Google's response below:
https://community.stadia.com/t5/Stadia-General/Response-from-Google-with-regards-to-delayed-activati...
Also you can check the 'Solution' on the pinned post on this board:
https://community.stadia.com/t5/Stadia-General/Ordered-6th-of-june-yet-to-recieve-a-code/td-p/255