I updated my username prior to e-filing my 2016 taxes and now I can't access my tax history timeline. Why do I need to go through all the hassle of getting a mailed transcript to obtain my 2015 AGI? I know the previous username and password and would not have changed it if I needed that #. Seems silly...
Its possible you may have created another username linked to your email which would inhibit you from accessing those previous returns.
The IRS requires the AGI number of your previous return as a new safety feature.
If you filed with us the year prior, you'll be able to locate your previous year's AGI in your TurboTax account.