On high gravity and especially high gravity heavy hopped beers you are always better off adding half a packet of dried yeast just to be sure. The yeast will not always respond as well on a natural conditioned beer after a high gravity ferment.
If you still don't get any carb in the next few days you can rehydrate a pack, take an eye dropper and crack open each one, add a little yeast and reseal. You should get carbonation then assuming you mixed the priming sugar up well.