Why am I not getting the $2000 per child under the age of 17? My annual for 2023 was $55K. I filed head of household and I have two dependents under the age of 17.

Do the children have Social Security numbers?   Are they showing up on top of your Form 1040 as dependents?

You do not "get" a refund of $2000 per child.  The most that can be added to your refund is $1600 per child.  That is the "additional child tax credit" which is refundable.  First the $2000 per child is used to reduce your tax liability to zero.  If your liability is at zero  then what is left of the $2000 per child can be refunded ----up to $1600-----based on how much you earned from working.  All of the child -related credits are based on income from working.

https://ttlc.intuit.com/questions/1900923-what-is-the-child-tax-credit

https://ttlc.intuit.com/turbotax-support/en-us/help-article/taxation/additional-child-tax-credit/L6xFeMFEf_US_en_US?uid=lqnuygah

https://www.irs.gov/help/ita/does-my-childdependent-qualify-for-the-child-tax-credit-or-the-credit-for-other-dependents

Look at your 2023 Form 1040 to see the child-related credits you received

PREVIEW 1040

https://ttlc.intuit.com/questions/1901539-how-do-i-preview-my-turbotax-online-return-before-filing

Child Tax Credit line 19

Credit for Other Dependents line 19

Earned Income Credit line 27

Additional Child Tax Credit line 28