The software just kicks back to the Wages and Income Main Page.
If you're using TurboTax Online, close the program, clear your Cache and Cookies, and return to the Retirement section to enter your SSA-1099.
Here's more info on How to Enter Social Security Benefits (SSA-1099).
I'm using Turbo Tax Desktop. I think it is a glitch in the software. I spent time on the phone with Turbo Tax this past weekend. They finally suggested that I reinstall the program. I did that and it still didn't solve the problem
You might reference this thread for a work around: https://turbotax.response.lithium.com/console/agent/16822203