things to check...
1) check the factions (find existing enemies for examples, though the default should be fine). Or try another npc type, there are many variations of each enemy type, some are passive / special for specific quests, etc. The draugr you're using may require an ambush event to wake up (try adding a spider or falmer or something to test)
2) if you've been playing with the terrain, you'll have to update the navmesh so the enemy can path to you for attack, otherwise they'll just stand there confused.