Average luteal phase is around 10 to 16 days, that means you probably ovulated between CD 11 to 17. Sperm can live up to 5 days in fertile cervical mucus, but more realistically up to 3 days only.
You would have a good shot at pregnancy if you ovulated on CD 11, 12, 13, 16 or 17.
Even with perfect timing, the probability of conception is only 25-30% for healthy couples every month.
It would help if you are tracking cervical mucus or using ovulation tests.