At the top of the fridge in the back is a small tube; remove it by unscrewing the screws that attach it to the back. The tube will slide out. You may find that it is filled with a solid core of ice. If that's the problem, just run water over it to remove the ice and put it back it place. We found this AFTER paying $60 for a new solenoid which wasn't the problem. Good luck!
There is a tube behind the fridge drip warm water on it ,it probably froze so you have to unfreeze it.