Can I file for child support as a adult child. I have no current claim for support. However a claim was attempted at the age of 16, but was dismissed. I am a child born out of wedlock. If I can't sue for child support. Can I file a claim on the estate after death of my father? Do I have to prove I am his child before death? Please help, this matter is confusing.

No first you have no standing to ask for child support only your parent or guardian can do that.
Your parent who had custody of you could have filed and they could have collected.

Yes you may file with probate upon their death. You will have to prove you are his child.
You have no legal way to prove that before his death.

Why was the case dismissed? As noted you can't file.

You could enter a claim against your father's estate, but if he left a will your chances are slim.