The "Mullion" wall does get warm (part of the Sealed System return line), but it may be hot because of an overheated Compressor.
The IceMaker won't work unless the Freezer is colder than +15F.
(could be caused by same problem)
Have you cleaned the Condenser (Compressor) Coils lately ?
Does the Condenser (Compressor) Fan work (when the Compressor runs)