There is nothing that can be done about this at this time but wait. And the email did not say you HAD to amend the federal return ... it said you MAY HAVE to amend IF the unemployment made you eligible for credits that were not reported on the original return OR if your state required it.
No one back then could have anticipated the unintended consequences with the issuing of the advance CTC payments ... not even the IRS knew what direction they were going to take. They are still making up the rules as they go ... look at the dates the FAQ's have been added to the list. https://www.irs.gov/credits-deductions/advance-child-tax-credit-payments-in-2021
