It is asking for your 2023 AGI -- that is how the IRS verifies that the same SSN is being used for 2023 and 2024.
Where do I find my AGI?
https://ttlc.intuit.com/community/agi/help/how-do-i-find-last-year-s-agi/01/25947
Your 2023 tax return shows your 2022 Adjusted Gross Income (AGI) If you filed a joint return then the AGI is the same for each of you.
Form 1040 line 11
If entering the amount from your 2023 tax return does not work, then try entering “0” instead. If that does not work and you still cannot e-file, then print, sign, and mail your tax return.
You can get a free transcript of your past return from the IRS:
https://www.irs.gov/individuals/get-transcript
Note: If you filed late or amended your return, your correct 2023 AGI may not be in the system.
"I am on SSI."
If your only income has been Social Security you are not required to file a tax return unless you have a 1095A for marketplace health insurance.
SSI and Social Security are not the same thing. Which did you have?
WHAT IS THE DIFFERENCE BETWEEN SOCIAL SECURITY BENEFITS AND SSI?
https://www.ssa.gov/ssi/text-over-ussi.htm
If you had SSI, you do not enter it on a tax return at all.