I followed all the instructions and solutions in Format Extra Storage for CCwGTV I have tried it with a number of different (brands) sd cards and usb sticks but each time after successful format when i choose to migrate i get a message
chromecast with google tv could not migrate to usb drive
Thanks for reaching out and sorry to hear about that. You could try to check this support website article to see more info on how you can expand your storage. Also, you may check this thread, it might help you with formatting your extra storage for the Chromecast with Google TV.