I had the same trouble, but learned all I needed from 2015 was my AGI. (I could log onto my account from last year, eventually, but learned that I had to pay the Plus membership to get a copy of the return - even though I had paid a premium subscription for 2016 on the new account!). If you need the full return, you will have to pay the cost for the Plus membership. To get just the AGI toggle through just as if you are going to file for 2016 under the old account and it will eventually take you to the place where you can get the AGI.