I had this problem too. Basically you are getting air not
through the intended side holes, but via bottom of the base where the battery contact is. Side air holes are covered up by the rubber grommet of the atomizer head and doesn't allow any airflow. Two ways to fix this.
DIY method is to cut flush the grommet on the atomizer. Take a sharp knife and trim it, so that it is flush to the metal. I do this to a few and worked great.
More permanent solution is to change the base with new AeroTank base. This not only fixes the blockage problem but also give you control over amount of air as well.
KangerTech AeroTank Base - Sun-Vapers.com