If you filed a 2020 return on time (that is, before May 17, 2024), and you claimed a rebate, but the rebate was never paid, then you should consider the possibility that,
1. The IRS paid a stimulus payment to you, so they removed the rebate from your refund claim.
2. The IRS included the rebate in your tax refund, but your refund was reduced for other reasons.
3. The IRS paid your refund including your rebate, but it was lost or misdirected.
Did you get your tax refund for 2020? Then you got what you are going to get, and form 3911 will not help. If there was a problem with your 2020 tax return, you had until 2024 to file an amended return.
Did you never get your tax refund for 2020? Is that because the IRS held it for other debts, or the check was lost in the mail, or it was deposited in the wrong bank account? If the refund was deposited in the bank account you told them, your case is over, even if you told them the wrong number by accident.
Most of this questions should be answerable by researching your 2020 tax return and your tax account by using the Transcript service.
https://www.irs.gov/individuals/get-transcript
If you never filed a tax return in 2020 (or filed it after May 17, 2024) it is too late to claim any refund for any reason.
