It's probably not because of the AGI. Did you get any of the 3rd stimulus last year starting in March? $1008 would be the reduced amount for going over the AGI. Was your AGI under 80,000 max for no credit?
The max amount is 1,400. So you had the 1,008 on 1040 line 30? You might have tried to claim it again. Line 30 is only if you didn't get the full amount or qualify for more. The IRS shows they already sent it to you.
Did you get IRS letter 6475 saying what they sent you? If you didn't get the IRS letter 6475 saying what they sent you then check your bank statements and check your IRS account to see when and what they sent you.
https://www.irs.gov/payments/your-online-account
If you didn't get the 3rd Stimulus check but the IRS shows they sent it to you then request a trace for a missing third Stimulus payment
https://www.irs.gov/newsroom/questions-and-answers-about-the-third-economic-impact-payment-topic-j-p...
