What does letter CP13 say? I haven't heard of that one. Letter CP12 is usually for the Recovery Rebate Credit.
Did you have 2800 on 1040 line 30? If the IRS took it off they show they already sent you the 3rd Stimulus payment.
The Recovery rebate credit on line 30 is only if you didn't get the full Stimulus payment or qualify for more.
Double check your bank statements and Check your IRS account (both accounts if married)
Your Online Account | Internal Revenue Service
If the IRS thinks they sent it to you but you didn't get it 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...
