First not everyone got the first payment yet ... if it gets mailed it could take a week to show up. And if your return is still processing that will also delay the payment. If you don't get all or any of the credit in advance then you can apply for it on the 2021 return. Check if you are eligible here :
https://www.irs.gov/credits-deductions/advance-child-tax-credit-payments-in-2021
https://www.irs.gov/credits-deductions/2021-child-tax-credit-and-advance-child-tax-credit-payments-t...
