To toggle mute unmute (Milo's microphone on/off), do one quick click in the center of the big round Milo button. Make sure you click rather than hold the Milo button.
If you hear battery information instead, that probably means you were holding the Milo in your hand, touching the power button on the back at the same time as you clicked the front.
If you hold the Milo button 1 second or longer, you will still mute your mic when you let go, but you'll also now be in push-to-talk (PTT) mode. In PTT mode, you hold the Milo button while you talk, then let go which again returns you to muted. To leave this mode, you click once on the Milo button, just like you would to unmute.
Note that in very cold temperature weather - we're talking colder than 20 below - you may find that it can get tricky after a while to click the Milo button. If so, temporarily warm up the Milo with your hand in a pocket or inside a mitten. You can also use a wired USB-C headset with a mic control button if that button works better in such cold temperatures.
If you still have trouble with muting, please contact us at support@okmilo.com