Sugar cane growth is based on random block "ticks" so under certain circumstances it could possibly take a long time. Also too, sugar cane will not grow if you are too far away from it, so that could be the issue as well. Hope this helps!
Also, make sure theres enough light for it to grow, enough room for it to grow (a few blocks above) and planting it on sand makes it grow faster as well. Hope this helped!