I had the same issue (using a Mac) and had to create another user on my Mac and use TurboTax from that user to get it to activate. I copied my tax file from last year to that user as well so that TT could import my old return information too. I was never able to get the software to work on my normal user, so had to complete the return and file from the dummy user. While I am on a Mac, I first saw this workaround from a Windows PC user, so I imagine it will work just the same. To be clear, the dummy user is on your computer ... I used my existing TT account user with no problem.
Hope it works for you.
