Most Sharpie Markers die an early death because you forget to cap them. Without the cap in place, the ink in the felt tip of the marker dries out, preventing the ink still in the barrel from flowing to the tip.
You can bring that marker back to life by dipping it into a dish of warm water. Remove it as soon as it is thoroughly saturated and then blot it on a dry rag or paper towel.
Continue to blot and massage the tip until the water has flowed into the fibers of the tip which will allow the ink to begin to flow back into the dried out tip.
Once the ink is flowing again, make sure to put the tip back on securely.