Let's separate 2020 and 2021.
For 2020, most likely no. Due to a 2015 law, certain tax benefits can only be paid if the child has a valid SSN that is included in an "on time" tax return. A tax return can be filed "on time" as last as October 15 of the year, as long as you get the automatic extension before the regular deadline (which was June 17, 2021 for 2020 taxes).
You probably should have filed an extension request and waited. If you filed the original 2020 tax return before June 17 and the amended return after June 17, you probably won't get the full $2000 child tax credit for 2020.
For 2021, you probably also won't be enrolled in the advance child tax credit payments for 2021. You may be able to enroll later in the year when the IRS adds that function to their web site. If you don't or can't enroll in advance payments, you should still qualify for the $1400 round 3 stimulus and the $3000 or $3600 child tax credit. Remember the advance child tax credit payment for 2021 doesn't change the amount of the credit, it just changes when you get paid.
