You are trying to enter the SSA-1099 in the wrong section of the 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
If you are trying to enter your social security benefits, you do not need to enter a TIN as this is a federal government payment. You will enter it under the retirement income section where it says SSA-1099. If you are entering it anywhere else, you need to delete the entries and enter it in the SSA-1099 section
To get there you can enter SSA-1099 in the search bar and click JumpTo SSA-1099