SM-N910P Why is Android Device Manager app not working on my Samsung Galaxy Note 4?

[AC Question]

I downloaded the Android Device Manager app and when it opens it shows an icon labeled SM-N910P and is says "unavailable" below it in gray letters. I do have Location Services On. When I press "Ring", it is supposed to ring your phone for 5 minutes, but nothing happens.
Please help!

 

[B. Diddy]

Welcome to Android Central! Go to Settings>Security>Device Administrators​, and make sure Android Device Manager is checked on. Does that make a difference?