Since you didn't file or pay for a 2018 program
under the same account that you used for the 2016 return ... then you have 2
options.
1) Pay for the 2018 program to unlock the
prior year returns
You have to start a
2018 return using the Free edition from this website - https://turbotax.intuit.com/personal-taxes/online/
(If you already have the Deluxe version or
better chosen then you can skip the upgrade and go straight to the payment
instructions)
You must enter some basic personal
information in the Personal Info section of the program.
Click Upgrade,
located near the top of your screen. In the pop-up window, scroll down to
the bottom, select TurboTax Plus, and click the Upgrade Now button. If you want to
include a state program with your order click on State Taxes and complete some
of the state section.
To pay for the upgrade so you can access
your prior year tax returns, assuming that you signed onto your 2018 account
with the exact same user ID you used for the prior returns -
To pay the TurboTax online account fees by
credit card, without completing the 2018 return at this time, click on Tools at the left side of the online
program screen. Then click on Print
Center. Then click on Print,
save or preview this year's return. On the next page, to pay
by credit card, click Continue.
On the next screen it will ask if you want Audit Defense, if you do not
want this option just click on the Continue button.
The next screen will ask for all your credit card information so you can
pay for the account.
2) Contact TT support and have them unlock
the return since you used another account for 2016:
Use the following TurboTax website to
contact TurboTax customer service/support
There will be some personal information
gathered so a case can be created for you. A phone number will then be
provided, specific to your case, to speak directly with a TurboTax agent.
https://support.turbotax.intuit.com/contact/
Note: The Call option will not be available when TurboTax
Support is closed.