Are you running a different account besides the admin account? If so, you might want to check that your account is set up to use 'View by Device Type' in its settings.
Actually I finally figured it out today. When I was looking at my Accounts (including my own) I noticed the Device View said "Missing", even though in the account it was set to "By Device Type".
I ended up having to go into each account, and change the view to "None" and save it. Then had to go back in, and change it to "By Device Type". This finally registered it for all accounts, and allowed me to then see the sample reports I had been creating.
All in all...a real head scratcher...particularly since I had no errors.