7. What to try if the M3 freezes or cannot be turned on?

A: First, please check if the M3 is sufficiently charged. You may try to connect it to a Power supply for around 10 mininutes or longer then turn it on.
If it still cannot be turned on after that, try to hold the Power button for at leaset 10 seconds to force shut it down, then turn it on again.  

If these methods wouldn't help, please try to contact your seller or FiiO (by sending email to support@fiio.net).