You are entering the SSA-1099 in the wrong section of the TurboTax program.
To enter Social Security benefits reported on form SSA-1099
Click on Federal Taxes (Personal using Home and Business)
Click on Wages and Income (Personal Income using Home and Business)
Click on I'll choose what I work on (if shown)
Scroll down to Retirement Plans and Social Security
On Social Security (SSA-1099, RRB-1099), click the start or update button
Or enter ssa-1099 in the Search box located in the upper right of the program screen. Click on Jump to ssa-1099
You may not be in the correct place to enter your Social Security income because that information is not part of your inputs.
Click on the magnifying glass at the top of the screen and enter 'social security income', then click on the link provided to go to the correct section of your return.