Please press Shift+Global, turn the encoder left to the display clockwise a couple of times and check if Blofeld has been accidentally set to MIDI Local OFF. Change it to ON.
Maybe you have used the Free Button with the Mute function. When the Free Button has been set to Mute and the button has been pressed, there is no other way to get Blofeld running again than by setting the Free Button to mute again and pressing the Mute button another time.