Why won't my mini cheesecake set?

I followed a mini cheesecake recipe online and followed all the instructions including setting time. It said let it set for 3 hours or overnight and i did overnight and next morning, i dipped a toothpick in it and it was a gooey mess! What do you think went wrong? If your not a expierenced baker or if baking isnt your thing, Please dont answer but if you can bake and cook or if your a good chef and/or baker please answer! THANK YOU SO MUCH!