Remove the lower 3 shelves (and food) in the freezer, then take out the 2 screws holding the center and lower cover on the back. You'll find the Maytag SXS manual in the front of the forum to show you how if this is not clear.
Once the center and lower rear panels are off in the freezer, you will see the drain pan under the cooloing coil has frozen over, causing all defrost water to go onto the freezer floor instead of down the hole in the pan. The solution is tp pour very hot water onto the pan to remove the chunk of ice then pour more down the drain hole unttil it runs by itself to the pan underneath. When you get it all back together, go to the fridge controls and set the top one just below midway, the lower slide just past midway to avoid freezing the drain again.