Another point not yet brought up is examine your draw technique while vaping.
A long, slow, and gentle draw (4 - 6 seconds long) works best. Imagine sucking on a straw in a thick milkshake. Use your cheek muscles to get a mouthful of vape. Do NOT do a hard lung draw, this will flood the carto.
If all else fails, I recommend starting from scratch after totally cleaning the tanks. Prime your carto using my detailed method described below. Insert the carto half-way into the totally assembled tank (don't fill the tank with the top cap off - this will flood the tank). Fill the tank carefully 80% full (careful to not get more juice into the pre-filled carto), then insert the carto the rest of the way into the tank. It should be good to go at that point. Getting a tank tool makes the whole process much faster and easier.
BADITUDE'S CARTOTANK SETUP GUIDE