There’s several things that could cause it These Linear compressor run on variable voltage of over 300vac, controlled by an inverter board part #DA41-00614B. To know for sure if the inverter failed, voltage tests are needed.
I would definitely return the board and put your original back in. If the fresh food section is cooling and the freezer isn’t, I’d begin at the 2way valve part #DA97-07070A. Your model has 2 evaporators that use the refrigerant separately. The 2 way valve sends the refrigerant to one evaporator for about 15 minutes, then it sends it to the other evap for 15 min repeating constantly. Sounds like the valve isn’t sending it to the freezer evap. You didn’t mention if the fresh food was cooling. Im only assuming it is.