Fridge works (or worked) but not the freezer
I would check your circulating fan, then thermostat probe. These are both located in the back of your freezer. You will have remove the covering to get to them. Take pics with your phone camera as you go. It will make it easier to put back together. As far as your new board not working, I know its hard to believe but, you can get a new board that is defective. Mine did the same thing and the fan would run, but not all the time. When I replaced it, it was working properly.