Well, I think you must have a defective unit. Keep on emailing or calling Herbalaire. They really have great customer service.
Don't put tobacco in with your herbs in the Herbalaire. There's no need and tobacco vaporizes at a much higher temperature too. You should be able to put a small amount in the crucible (half full max) and when the light turns yellow, start inhaling slowly. After the first inhale, you should be able to see vapor when you exhale.
The only thing I can think of is that you got a defective unit. It sound slike you're doing everything right.
Don't despair, talk to Herbalaire about the problem and they'll help you out. Sorry I can't provide any more help. Good luck.