But what if your device is not displayed in the device manager? Allow us to show you how to fix it.
We faced this issue on a Nexus 4 and apparently we were not alone. This could be specific to Google’s phone too, since all our other devices worked perfectly with ADM.
Avinash posted about the problem at our forum and we fixed it by following these steps:
1. Open the App Drawer on your device and tap the Google Settings Button (Green one with the gears symbol)
2. Tap on the last option there “Android Device Manager”, you will find two options there.
3. Disable “Remote Factory Reset Option”
6. Re-enable the factory reset option under the Google settings.
Now the device should be displayed under the Android Device Manager webpage.
via Google Forums.
Let us know if it worked for you.