Are you using the actual Turbo Tax Social Security worksheet in your return? To see the Social Security Benefits Calculation Worksheet in Turbo Tax Online version you would have to save your return with all the worksheets to your computer. Or if you are using the Desktop CD/Download Software you can switch to Forms Mode (click Forms in the upper right) and click on SS in the list on the left side.
Then are you using the IRS Pub. 915 on Social Security. There is a blank worksheet on page 16
https://www.irs.gov/pub/irs-pdf/p915.pdf
