The multi-knob does not change memory channels when in memory display on the face of the radio. Use the Up and Down buttons on the radio or on the microphone to change channels in this mode. 

 The Multi knob changes channels when the radio is in channel list mode. To access the memory channel list, press the multi knob (push it in). - I got this to work once and now not again.  Access the Memory List by pressing Menu | Memory.