Yes, you can amend your return if you are certain you qualify for the Child Tax Credit and did not receive it, but it is too soon to amend. You should wait until the return is fully processed. If you are expecting a refund and are amending for an additional refund, the IRS states you should wait until you've received the original refund. Then, you can amend as soon as the federal amended tax return form 1040-X is available for filing in TurboTax. Use this tool to check availability of forms, including 1040X: Tax form availability
Here is some more information on filing amendments: How to File an Amended Tax Return with the IRS
If your child was 17 before the end of 2024, you do not get the child tax credit. You only get the child tax credit for a child who is younger than 17. After they are 17 you get the $500 credit for other dependents.
Earned income credit is a different credit and is not limited by a 17th birthday.
If you entered something incorrectly for a qualifying child then you can amend after your original return has been fully processed.
You will want to go through the screens in MY INFO to make sure you entered things correctly for a child who was under the age of 17.
Make sure you have entered your child as a dependent in My Info, and that you have entered the child's Social Security number. Careful— do not say that your child’s SSN is not valid for employment. If your child was born in 2024 make sure you said he lived with you the whole year. There is an oddly worded question that asks if the child paid over half their own support. Say NO to that question.
Do not try to make any changes to your return while it is in pending or while it is being processed.