Recessed Lighting Stopped Working
Recessed light that are for incandescents have a built in thermal detector, over the years the eventually give up and the can stops working. The outside has more extreme conditions so it stands to reason they would give up first. The detectors are generally located on the exterior of the can. If these cans are original installations and not remodel cans, you can actually remove the small screws towards the bottom of the can. You may have to remove the trim first.

Once that is done you will be able to see the detector on the side and the junction box mounted on the can frame. This box has snap off covers so you can get to the wiring. Check to see if you have power to this box.  Unfortunately they stopped making replacement thermal protectors so you will need to replace the can, if you find power in the box. If you do not have power in the box then I am afraid the only way you can find the problem is to track it down (see Michael Karas).