Hi, I have the newest model, THI20, and I am now on the 18th day, so I will be stopping it from turning the eggs in about two hours.
If you find that it is not turning, first about six inches one way and then about six inches the other way (Tape a piece of paper on the gray part outside and watch it for about an hour), in the instructions you will read that you need to take an allen wrench to the hole in the bottom of the red part and tighten the screw that's up inside. WARNING, DO NOT TURN THE RED PART UPSIDE DOWN; YOU WILL LOSE THOSE TINY, TINY BALL BEARINGS. If you MUST tighten the fitting in the bottom with an allen wrench, have someone hold the entire incubator up or balance it on the edge of a table while you tighten it, but DON'T turn it upside down.
I'm betting though that it is turning, and you just can't tell it. I sure hope this Brower is as good as I'm thinking that it is because so far all I've had to do is add a cup of water every other day. It's maintaining 99.5 degrees perfectly, and it gets it back to 99.5 quickly after I remove the lid for whatever reason. I sure hope that the fan is maintaining the humidity as well as it is the temperature. I've no way of testing humidity; the instructions just say remove a plug on the top three days after incubation starts, and then remove plugs the last three days if water drops form on the cover and again after hatching begins.
Call me at 317-535-5855 if you want to discuss the allen wrench business.