Very strange. For me stuff like that works.
what window version do you use?
Besides, whenever i plug my device to the usb, the device prompt me for password, is this normal?
Even i do not enter the password, i can still use mtp to transfer file.
I just would like to share a solution which worked for me about USB debugging :
Enable USB debugging from Settings > Accessibility > Developer options
On the PC, open Device manager (right click on This PC >Manage > Device Manager)
Under Other devices, you’ll see _MX4… (_with yellow triangle containing an exclamation mark).
Right click on it > _Update Driver Software > Browse my computer for driver software > Let me pick from a list of device drivers on my computer > _search/select _Samsung Android ADB Interface > _click _Yes _when _Update Driver Warning _message box appears
Note : notice if you develop Android Applications using Android Studio, make sure minimum sdk version defined in “your project”/app/build.gradle file (“minSdkVersion XX”. XX is the version number) is under your MX4 API’s version.
I just put it to 10 while my MX4 API’s version was 19.
Solution by Rolm solved it for me on Win 8.1. Pro 64-bit.
The drivers supplied by Meizu directly from the device when changing Storage mode to CD-ROM does NOT work. The Google USB driver doesn’t work with the MX-4 either, it does however, work with my Nexus 7 though.