Is only the first glass warm?
If water is not being used very often the first glass of water may not be as chilled. To avoid freezing in the water line, many refrigerators run the dispensing water line from the cold water source through the outside of the product. Therefore, the water being dispensed may be warm at first, then get colder. If the second glass of water is cold, the unit is performing as designed.
Was the refrigerator just installed?
Depending on the model, it can take up to twenty four (24) hours for the water to properly chill after installation.
Was a large amount of water just dispensed?
If a large amount of water was just dispensed, it will deplete the water reservoir. The new water needs time to chill. Allow time for the new water to properly chill (time depends on model).
Is the refrigerator connected to a cold water supply line?
Verify the unit has been hooked up to the cold water line. Installing the refrigerator up to the hot water line will cause the unit to dispense warm/hot water.