Are you trying these steps on Linux or on Windows host ?
If this is on Linux, can you try the following:
$sudo adb kill-server
$sudo adb devices
Now try installing the apk.
Reason: The adb server has to be started with root privelages for adb devices and adb install commands to work. The above commands will make sure its done.
If this is on Windows, can you share a screen shot of your DeviceManager window (showing the Device enumeration type).
Full Disclosure: I am an employee of Qualcomm Innovation Center, Inc. San Diego . Views expressed are my own and not reflect my employer.