Did you get both the 1st and 2nd Stimulus checks? Are you Single? The second round was $600. Did you get that one? If you claimed a missing stimulus payment on your return but the IRS took it off you have to ask the IRS. They think they already sent it to you. Maybe it went to an account you don't remember. Or you got a check or a card. It was probably easy to miss the debit card in the mail and think it was junk mail. They have to put a trace on it.
IRS for Payment Issued but Lost, Stolen, Destroyed or Not Received. See question F3 here, you can expand it to see how to put a trace on it.
https://www.irs.gov/newsroom/2020-recovery-rebate-credit-topic-f-finding-the-first-and-second-economic-impact-payment-amounts-to-calculate-the-2020-recovery-rebate-credit