@DickM. This thread has been discussing the fact that Sofabaton removed the LONG PRESS option on some buttons (Direction, Volume, Channel & Mute) not the operation of the Mute button itself. If you are having problems with Mute itself that is a different issue and it may be worth starting a new thread. But on my X1 the Mute button itself works as it should (press to Mute, press again to unmute).