David,
Tell us more. What's the dry-bulb when you are trying this? What wet-bulb do you achieve? What do you use for a dry-bulb setting and are the heat valves open?
Several possible reasons -
There's not enough steam spray.
The wood is cold and the vaopr condenses.
The kiln leaks too much.
The kiln is not well insulated and the vapor is condensing on cold spots.
The dry wood is adsorbing the vapor (less likely).
The first reason is most likely. Make sure the line is not restricted. These line plug occasionally.
Mike M.