Hi walt_farrell
Welcome to the Norton Community Forums. 
As you have Norton 360 Multi-Device you should be able to use the
new version of NMS 3.0 on your Android device.
So you would have downloaded the apk for NMS from the Norton servers
and installed and activated NMS. Now version 2.5 of NMS being the
full paid version allows the user to download and install the free addon
Norton Anti-Theft plugin which you are having issue with. :-(
If you still have available installs and have not installed N360M-D more
than 4 times as you have 5 installs to use for PC, Mac or Android, you
should be able to uninstall NMS 2.5 from your device and also the
Norton Anti-Theft Plugin, and then install NMS 3.0 as part of your N360M-D
subscription and available installs.
NMS 3.0 now has it's own new web based Control Panel for remote commands
like Lock, Scream, Locate, Sneak Peek and Wipe, more info about the NMS 3.0
Control Panel at this link- http://mobilesecurity.norton.com
Just means only 1 app is needed being NMS 3.0 and no more need for the NAT
Plugin.
Now you can download NMS 3.0 from the Google Play Store, just search
for Norton Mobile Security or use this link here .
Now open the NMS 3.0 app and sign in using the Norton Account details
that are linked to you N360M-D product.
If needed you may have to select upgrade then the option i have already
purchased the product and your upgrade to the full version of NMS 3.0
should be done.
The remaining days of your subscription to N360M-D should be the same with
N360 on your PC and NMS 3.0 on your Android device.
Let us know if you require and more info or assistance and keep us posted on
how you go.:smileyhappy
Cheers. 
EDIT- Appologies it took so long to reply as i did miss this thread in the forums.