See the TurboTax support FAQ for completing a prior year tax return started with the online editions - https://ttlc.intuit.com/questions/2559403-how-do-i-finish-a-prior-year-return-that-i-started-in-turb...

If you paid for the 2016 online account with a credit card then you will need to contact TurboTax support and speak directly with support agent.  They may be able to push a 2016 desktop installation file to your download account.

See this TurboTax support FAQ on how to contact Support - https://ttlc.intuit.com/questions/3401489