I had a similar problem with my Nexus 4(Android version 4.4.2), it wasn’t listed in adb devices.
Make sure USB debugging is enabled from device, and do the following on your PC:
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Update Android SDK (Google USB Driver)
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From PC Control Panel, System -> Device manager -> Right click Nexus 4 -> Update driver.
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Set android-sdk-folder\extras\google\usb_driver as path to search, include subfolders checked.
If windows tells you that the driver is up to date, just uninstall the driver (right click on nexu4 -> uninstall driver) and start from step 2 again.
After that, open a cmd and type adb kill-server and then a adb devices, now it will include your device.
https://developer.android.com/studio/run/oem-usb.html