Dear MIKE 130,
after doing some research, I agree that someone who has a residence permit according to section 19d of the AufenthG is in principle entitled to child benefit.
I have looked up reasons for the refusal of Kindergeld despite this type of residence title. On
https://familienportal.de/familienportal/familienleistungen/kindergeld/faq , a website of the Federal Ministry of Family Affairs, I found the following information:
Firstly, you may be only entitled to Kindergeld if your children also live in Germany (or if they live/are registered in another member state of the European Union (EU), Iceland, Liechtenstein, Norway or Switzerland).
Secondly, child benefit might be refused if you already receive a benefit similar/comparable to Kindergeld (e.g. from another state).
Thirdly, your child must not be over 18 years old. If your child is unemployed, Kindergeld is paid until they turn 21. If your child is undertaking vocational training, you will receive child benefit until they reach the age of 25.
If you have any questions regarding this issue, I recommend the above mentioned website where the information is provided in English (and several other languages) as well.
Kind regards!