I also have a number of protanks, which I love, in spite of some of their quirks. Sometimes, the atomizer units are not the best and provide lousy vapor brand new out of the box. The nice thing is, the atomizers are inexpensive, and can be rebuilt to your preferred setup.
The first thing I would check is the voltage, as previously mentioned. The Kangers prefer the lower voltages. Another issue is the e-liquid used. They will not handle mostly VG liquids well, and if you are using mostly VG, you may need to thin it for the Kanger to wick properly. When set up correctly with the right juice, it should produce clouds of vapor.