I am 24yrs old my father isn't on my birth certificate I asked someone whom may be my potential father to take a paturnity test and he declined I want to test to be done just for GP not child support or anything what can I do?

Honestly, very little.
Why are you so determined to have this test done at this time in your life ?
Have you asked your mother who your father is?

What is "GP"? What evidence is there that he is your father?

GP means "general purposes" I believe

I'm puzzled that you would think there is something you can do under the law.
It's fine to ask, but invasive otherwise. And we don't know how well you know him, what basis you have for your belief that he is your father, and how you presented your question.
For all he knows you want to get involved in his life in a way he doesn't want, or even sue for his estate when he dies.
If this is vital to you for some reason, why not get to know him better for a while? But it sounds like it's too late. He's probably wary now.

What State are you in and is the supposed father in the same state or a different one ?

GP means "general purposes" I believe

Yes, that could be it, in fact, that was my thought, but it might not. So why guess? Why not let the OP answer and tell us?

Honestly, very little.
Why are you so determined to have this test done at this time in your life ?
Have you asked your mother who your father is ??

Sorry it has taken so long for a reply.. Well, the main reasons for me finding out whom my real father may be is because of medical reasons and I would like to get to know what my father is like.. I grew up with my mom telling me that this one guy was my father and there was a paternity test done with out me knowing and I just recently discovered that my mom knew this one guy wasn't my dad and knew for 7yrs and never told me I found out threw a family member so basically I'm just hurt by the situation and I would really just like to meet who my biological father is and get to know him his family and learn about my other half medical issues etc.. So I didn't know if there is a way I can get the guy whom my mother claims it maybe to take a paternity test thanks for your suggestions xo

What is "GP"? What evidence is there that he is your father?

My mother told me that he was the only other person she was with at the time any suggestions on what to do?

(I thought GP meant General Practitioner, but we still don't know exactly.)

You also haven't answered other questions above. We don't even know if your mother is alive, and if you have asked her to contact him.

There isn't anything you can do if he won't agree to the test.

and I would like to get to know what my father is like.. ... so basically I'm just hurt by the situation and I would really just like to meet who my biological father is and get to know him his family

Forget it. You cannot under any circumstances, force him or his family to be a part of your life. If they don't want you a part of your life, then that's it.

On the other hand, you are entitled to a medical history. Do you know of any issues in your health or his that might be an issue? You can try requesting a medical history from him (better through a lawyer than from you personally) and going to court to obtain it if he refuses. If he denies paternity the court may then require a test.

As to your resentments, your mother may just have been trying to protect you. Have you sat down and discussed this with her?