Why isn't Kharjo appearing?
First of all, you should read How do I find my follower if and when they leave me?
Kharjo's home (spawn) is Ahkari's Caravan, which roams the route between Dawnstar and Riften. The fastest way to find it is to fast-travel to the same two cities, in their route, and keep checking the stables. Alternatively you can advance time by using the Wait feature.
Eventually his caravan will come to you.