Social security benefits (6a) not shown?

There is not a Box 6a on a SSA-1099.  There is a box 6 which would have the federal taxes withheld, if any.

Did you enter your Social Security SSA1099 in the right place?  If you entered it as a 1099R by mistake that is why you are not seeing it on line 6a.

Go to Federal> Wages & Income>>Retirement Plans and Social Security  (SSA1099 and 1099RRB) to enter your SSA1099.

If you entered in the wrong place you will need to delete the incorrect entry.

Oh, you are referring to Line 6a on the Form 1040.  If you did not enter your SSA-1099 in the correct section of the program then Line 6a would not have an entry.

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