Some of these freeze up in the door. Disconnect it at the bottom behind the kick plate and see if the water comes out there. If it does, its frozen in door. I use a clean Zoom spout oiler filled with hot water to squirt water into the dispenser tube to thaw it out.
There is a heater kit available for some of them. Also make sure the filter isnt old, if it has one. I carry a filter bypass with me.