pad mute is only for internal akai progs (drum/keygrp), doesn’t work with MIDI since there are no concept of “pads” for MIDI progs in the same way as for the int progs.
however, track mutes still work, so you always have the option of “expode tracks” to get all 12 note rows to separate tracks, and then you can mute em one by one… There are 128 tracks, don’t be shy