According to this link the wiring diagram for the freezer is A14353601 (see bottom of sheet for wiring diagram number, the service sheet number i.e. A14365701 is at the top of the sheet.
This shows how to enter the service mode for the freezer.
If the condenser fan is OK you need to check if the evaporator unit inside the compartment behind a panel is getting icy cold and that the DC evaporator fan is operating. The evaporator fan is used to drag air across the icy cold evap unit and blow it throughout the compartment to cool it down the set temp. The fan will stop when the door is opened and start again when the door is shut.
Here’s a link to the parts for the freezer, showing the evap fan (#28 cabinet parts diagram) and the switch (#45 cabinet parts diagram).
If the evap fan is iced up then there is a defrost problem. This could be caused by a faulty defrost heater, faulty defrost thermostat, blocked drain from under evap unit to the evap pan under the freezer or a faulty control board. The service sheet show how to manually test the defrost.