Are you using the Online version? The Online version is only for the current tax season which is 2016.
To prior a prior year return you need the 2015 Desktop version of TurboTax. Prior year returns must be mailed. You can purchase the 2015 Desktop software from TurboTax at the following link
https://turbotax.intuit.com/personal-taxes/past-years-products/
You can also check a website like Amazon.com for prior year TurboTax software for a possible better price.
