Upper ice maker not cooling

Over the weekend, I turned the power off to my refrigerator to replace the lower icemaker in the freezer. Up until that time, the in-door icemaker up top worked perfectly. After turning the power back on, my freezer and refrigerator are cooling perfectly, my new lower icemaker is making ice perfectly, but now, for some reason, my upper icemaker will not cool off and freeze the water. The upper icemaker is cycling and loading water properly, it is just no longer getting cold in the compartment and freezing the ice. I waited at least 48 hours and still no ice freezing in the door. I am at a loss at what to try next. Any help in my next direction would be appreciated!