Phone not appearing in Android Device Manager

When I go to Android Device Manager, my tablet is listed, but not my phone. I had signed up just as soon as ADM was available, and at that time both devices were listed. Now, for the last several days, I can only see my tablet. (For what it's worth, both devices appear in the "My Devices" section of the Google Play Store.)

I have done the following while troubleshooting:

• Ensured that the Android Device Manager settings in Google Settings are both on. I have even toggled them off and back on again


• Ensured that Location Services are on


• Ensured that all sync services for my account are toggled on and work



• Have connected to the Play Store several different times


• Ensured Google Play Services is at the latest version


• Made sure I'm using the right account. (In fact, I removed the other secondary accounts from the phone)


• Power-cycled the phone several different times

I could understand if ADM couldn't find the phone due to it being off, out of range, poor signal, etc., but ADM would at least display the phone and tell me it couldn't find it.

So, any suggestions to get my phone to show up on Android Device Manager?

I would like this to be working before something happens to the phone. (Murphy's Law and all that.)

Although it shouldn't make any difference:

• Tablet: Nexus 7 (2012) with Android 4.3


• Phone: Verizon Galaxy Nexus with Android 4.2.2

Addendum:

There's apparently some (relatively new) advice on the Android Device Manager help page:

1. Open Google Settings from your device's apps menu.


2. Touch Android Device Manager.


3. Uncheck Allow remote factory reset.


4. Go to your device's main Settings menu, then touch Apps > All > Google Play services.



5. Touch Clear Data. Note that this action doesn't remove personal data.


6. Go back to Google Settings and select Allow remote factory reset.


7. Restart your device.

I have followed these steps, but it doesn't appear to have worked.

Answer

Well, I don't seem to have an answer why this was happening, but I got some advice about how to finally fix it.

From Ryan Lestage on Google+:

1. 
   
   

   Clear data for the following apps:

   
   
   
   
   • Play Store
   
   
   • Download Manager
   
   
   • Google Services Framework
   
   
   
   


2. 
   

   Restart your phone.

   
   



3. Fire up the Play Store app.


4. Wait for the device to show again on the web Play Store. It will appear under Settings > Devices. It may take a half-hour to several hours to appear.

When your phone has shown up in the Play Store with the date registered as today's date, proceed with the next steps, but not before.

1. Open Google Settings from your device's apps menu.


2. Touch Android Device Manager.


3. Uncheck Allow remote factory reset.


4. Go to your device's main Settings menu, then touch Apps > All > Google Play services.


5. Touch Clear Data. Note that this action doesn't remove personal data.



6. Go back to Google Settings and select Allow remote factory reset.


7. Restart your device.

I would like to know exactly which of these steps was the magic sauce, but I'm content that it worked at all. I suppose that Play Store connection makes some sense, because while my phone was listed there, it showed a "Last Used" date back in March or somesuch.

I really hope that the setting sticks this time, and that I won't be forced to repeat this process every couple of months just to protect my device. (If so, I'll go back to some of my other options, like Carbonite and/or Lookout.)