Is your plant quite young, like a year or less? If so, it is normal for young trees to be out of synch with the seasons and start putting on main crop figs too late to become ripe before cold weather sets in. You could use the greenhouse to extend the season but would the cost of heating the greenhouse be worth it for a few figs off a young plant? Generally, it is good to allow young plants to put on growth and develop their root system and not put energy into producing figs. For a first year plant I typically pull off all but one fig and then only leave one on if there is a chance it will ripen.