Fig tree die back
Freezing temperatures during the winter is the main cause of fig trees dying back to the ground. You didn't say which variety of fig that you have, but not all are winter hardy to our zone. Two varieties (and there may be others) that may do better here are 'Celeste' and 'Hardy Chicago'. Figs, especially young ones, can be grown in containers and brought indoors during the winter at least for the first three years. This helps to establish a healthy root system. Then they can be planted outside. Since yours is already outside, it needs to be insulated during the winter. I don't know what you have covered it with, but chicken wire placed around the tree and then filled with leaves should protect it. If we have a severe winter, there is a possibility that some damage or die-back can still occur.
One thing that you might try to help the ripening process along is to pick the figs off branches that are farthest away from the trunk. The less figs on the tree, the more energy will be directed to the remaining figs. Make sure your tree is fertilized during the growing season. If it doesn't have enough nutrients, the figs won't ripen. Also, check to make sure that your tree is not suffering from any pests or disease. All of its energy is being directed to healing rather than ripening. If you suspect pests or disease, take a sample into the Cooperative Extension Service to identify what is going on.