I've never had a problem getting vapor with mine (except when I forget to turn the pump on). I don't know if you have the new, thinner herbalAire bags or not (they told me they were getting rid of the thick bags), but the thick ones didn't get a real tight seal on the connector, and if you left the bag on too long during the fill process, the vapor would leak out. Even so, you should be seeing vapor going into the bag. Even thin vapor, where you hardly see it in the bag, should give you good hits that you can see (in the right light) on exhale.

I would contact herbalAire if you continue to get no vapor. Brown remains is a sure sign of vaporization, so you just need to figure out where your vapor is going. herbalAire has great service, so I'm sure they'll get it figured out or fixed for you.