Do you hear a fan in the freezer?
Do you see frost on the back wall of the freezer?
The most likely cause will be the defrost heater. With the unit unplugged use a hair dryer on low and defrost the ice. Becarefull with the hair dryer and the water. Have towels handy incase there is more water than the drain pan can handle. Once it is defrosted it will work fine for a week or more.
This is the heater assemby and the most likely cause. You can unplug and remove this to have it tested or if you know how to use a meter you can check it. Do not touch the glass.
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