Surgeons want to know the answer to this question, too. So studies have been done trying to link characteristics of patients who had a failed result. They've looked at age, size of tear, and how long between the injury and the repair.
Some studies show a better healing rate when the tear is small and repaired quickly. Others don't show the same results. Most studies have not been able to show any significant factors in meniscal healing.
The one exception is the patient who tore the meniscus and the anterior cruciate ligament. Repairing both at the same time seems to help meniscal healing. This is probably because there's more bleeding and clots forming. This seems to help meniscal healing.
For the moment you are indeed part of a small number of people who didn't get the results they hoped for or expected.