Many people complain from this because MANY phones are sold DEFECT. I bet you bought your phone from aliexpress. I had the same problem and i contacted Meizu official representative. They told me aliexpress is not official reseller so no warranty for the phone. I wrote to the seller from aliexpress and he told me to update firmware to fix the problem, but the firmware doesnt want to update. I download the latest and it dont install. No idea why. I think its something with the bootloader which is chinese…
So i think the only fix is to order a new home/fingerprint button with sensor and replace it.
Shame na MEIZu for that. Im sure thousands of meizu phones are sold in aliexpress … many with defects
My mBack button is not working either but until I manage to fix it I have found a way to go back through ¨Smart Touch ¨( under Accessibility in the config menu ) . You just have to set it to “on” and choose bellow under "Characteristics " the first option " Back " . Believe this is better than waisting your time reinstalling new Firmware ,etc. Of course If I manage to fix my mBack button I will let you know ! Regards