This is a common scenario. Reboot your Android studio and reconnect your device.
I had the same problem, except that I worked with it using the Android emulator. I realized that if you put the computer into sleep mode when Android Studio or the emulator is running, it will ruin the connection between them. My problem disappeared after restarting both, emulator and Android Studio.
capt.swag May 01 '16 at 6:37 a.m. 2016-05-01 06:37 a.m.
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