If you only get ssi or SS or SSDI  it is not taxable and you do not have to file a return.  And there is no benefit in claiming dependents or deductions.   Unless you have federal income taxes withheld from the benefits or you get health care insurance through one of the state marketplace exchanges and receive a Form 1095-A then you need to file a tax return.

And you can't efile a return with no taxable income.  If you want to file you will have to print and mail it.  Or you can try adding $1 of interest to let you efile.  Make up a fake 1099Int.

Enter a 1099-Int  under

Federal

Wages & Income

 Interest and Dividends

Interest on 1099INT - Click the Start or Update button

Put the interest amount in box 1

TO ENTER Social Security .  Did you get a SSA-1099 ?

Enter a SSA-1099, SSA-1099-SM or RRB-1099  under

Federal Taxes on the left side or top

Wages and Income

Then scroll down to Retirement Plans and Social Security

Then the second line - Social Security (SSA-1099. RRB-1099) - click the Start or Revisit  button

2020 1040 line 6a is the gross Social Security amount and 6b is the taxable part of Social Security.

Up to 85% of Social Security becomes taxable when all your other income plus 1/2 your social security, reaches:

Married Filing Jointly: $32,000

Single or head of household: $25,000

Married Filing Separately: 0

Oh, the 1040 is the form you are filling out and entering your info into.  You enter your SSA-1099 and any other income you get or the fake $1 interest on 1099INT and Turbo Tax fills out the 1040 for you.  You file the 1040 with the IRS either by efiling it or mailing it.  

Why are you trying to file if you just get SSDI?