I got a similar problem. Except, I got my thermostat set to 34c (recommended for a spotty apparently) but on my thermometer, it reads 27-29c. Its been plugged in for over 24 hrs so one would think it be warm enough by now. It's a 600mm x 300mm x 300mm so its a fairly small tank. I have a heat mat that takes up between 1/3 and 1/2 of the floor. The heat mat is under the bottom of the glass tank and I have about an inch of bark on top. The heat mat is plugged into my thermostat. I also have a UV light that is about the heat mat (at the top of the enclosure). My thermometer screen is outside the enclosure but the actual thermometer stick is mid way between the bark and the glass that has the heat mat under it. I'm 100% sure I have it set up correctly. Some things just don't make sense in this world :S