IRS interview to help determine who can be claimed:
https://www.irs.gov/help/ita/who-can-i-claim-as-a-dependent
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 2023 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.
If she is still not showing up as a dependent, sometimes it helps to just delete her and then re-enter her as a dependent from scratch.