If your son was 18 by the end of 2021, no, you do not get the child tax credit. For a 2021 tax return you can get the CTC for a child who was YOUNGER than 18 t the end of 2021. You can still claim him as a dependent and you will get the $500 credit for other dependents for him.
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**