Android Studio (Windows 7) does not detect ASUS Zenfone. Cannot run my app
You need to turn on the USB debugging for ADB to work.
To turn on USB debugging:
Navigate to Settings > About Phone > scroll to the bottom > tap Build number seven 7 times. You'll get toast saying that you're now a developer. 2. Go back and now you can see  the Developer options in settings, check 'USB debugging' and click OK.
Some times you may need to install drivers for your phone. You can download it from manufactures website.