Relax. If you have to smoke a cig or two, go ahead. If it's flashing red, you have a prob. If it's flashing green it's almost always a coil prob. The unit has a built in electronic ohm reader. If you have a bad coil, which can happen, it will flash green. If the air flow is obstructed it will flash green. You have to line the coil up almost perfectly between the slots and push it all the way in until it seats. If it's not fiully seated it will flash green, because the connection isn't complete. As Trig said you can sometimes bump it with the charger and take a drag to see what happens.
Start over slowly. Take the tank off the battery. If you didn't fully charge it before, plug the battery into the charger. Take the top off the tank, pour the juice back in the bottle. Unscrew the bottom and take it off. Pull the coil out. Now you have it all apart. While the battery is charging, clean all parts of the tank with warm water and dry them off well.
Now, put the first coil aside and unpackage the extra coil that comes with it. Blow gently thru it to make sure it's clear. Wet your fingers and dampen the outside of the coil above the threads. This will help it slide into the o ring and seat. Take the tank and put it on a table with the bottom end up. Take the coil and insert it into bottom of tank. Carefully line up slots in coil with slots in tank bottom. Push. If you wet the outside of the coil a bit on the bottom it should slide in and seat, but you have to put a little push to it. Make sure it's all the way in. Next screw the bottom cap on. Just finger tight, you will feel it stop when it's snug. When the battery shows green it is fully charged. Take battery off charger. Take a q tip just damp with alcohol and clean the brass 510 pin in the top of battery. Dry it with some paper towel. Make sure bottom of tank is dried off. Screw it onto battery, just finger tight, don't crank it down hard.
Put unit back on flat surface.
Fill tank by running it down the outside of coil, don't put it in the middle hole. And don't fill it so full it goes into middle hole. Just fill it to top of glass. Put top on, screw it finger tight. Put tip in. Set it aside for 15 minutes.
Pick it up, don't fire it, and give it several dry hits. Set it back down for 10 more minutes. Pick it up again, give it a few more unpowered hits.
Then, 3 clicks on. Hit the fire button and draw.