YOU can go online (when it is working) and put the child in for the advance CTC payments OR just get the credit on the 2021 return when you file it next year.
What is more important is that dad MUST OPT OUT NOW of the advance payments so that he doesn't get caught with having to pay them back on the 2021 return. https://www.irs.gov/credits-deductions/advance-child-tax-credit-payments-in-2021
