My single mini cheesecake wont set.?!?

I made a single mini cheesecake and followed all the ingredients including setting it. The instructions said it didnt have to be baked. I let it set overnight, next morning i dipped a toothpick in it to see if it hardened and it was a gooey mess! I dont know what i did wrong. Please help me, especially if your a professional chef or talented baker. thank you so much.