Follow
this FAQ if you have access to the TurboTax Online account you used to file
last year.
https://ttlc.intuit.com/replies/5574744
Take a
moment to look over this FAQ to ensure you are using the correct field for your
2015 AGI
https://ttlc.intuit.com/replies/3301618
If that does not work for you, you can request a transcript from the IRS to make
sure you are inputting what the IRS has on file for your AGI.
https://www.irs.gov/individuals/get-transcript/