If you have the desktop version of the software, you should be able to go to View->Forms (upper left), and click on the Social Security Benefits Worksheet to see how the computation for the taxable amount of SS was done.
On the online version, you can go to My Account (top just right of center), then click on Tools, then View Tax Summary. When you see the 1040 summary, look at the top menu bar and click on Preview My 1040.
Here you will be able to see (on lines 20a and 20b on the 1040) the amount of the SS and the taxable amount, but I don't think you can see the worksheet until you pay for the product.
Note that there are a few other possible considerations in the calculation besides SS income and other income. See IRS Publication 915 and look for "Are Any of Your Benefits Taxable?".
Perhaps one of the other items is tripping you up.