It is registering the controller is connected, but will not let me play the game. It then takes me back to registering on the Chromecast. I'm frustrated 😒. Finally have my gaming controller and am unable to use it. I'm super close to returning it.
Since you're just now looking for your code, I'm assuming you still have the packaging your Chromecast and controller came in. You should be able to give Google store support the serial number off of that packaging and if it hasn't already had a code used for that serial they'll probably be able to help you. If you don't have your order number they should be able to identify your order if you can give them basic information that was used for the order... Name, address, email etc.