2 tablespoons of micronized kava should be enough to start feeling the effects. I usually only consume 4 tablespoons total micronized in an evening kava session. I recommend you try another tablespoon or two worth. I mix 1 tablespoon to 1 cup (8 oz) of water, but the ration shouldn't matter too much with micronized because you are consuming all the material anyways. I drink about half a cup every 10-15 minutes, maybe starting with a whole cup to get the things rolling along.
You could also be experiencing "reverse tolerance," meaning it takes your body some time to understand what to do with the kava. Are you completely new to kava? or just trying micronized Mahakea for the first time. I have GHK's Mahakea and like it a lot, one of my favorites of the half dozen types I have tried.