"The best business telephones in the world."

I'm having a difficult time getting Presence to function they way I expect it should. Perhaps the way I think it should work isn't how it actually works. BLF seems to function properly though. 

My understanding of presence is when I setup the function key on the phone it monitors the extension I put in the settings. It will show a green led when that extension is online and available and red when its in a call. And I should be able to push the programmed button and it will ring that extension. 

BLF Works 

When I setup BLF I see the other programmed function keys light up with an incoming call comes in. The function key lights up red when another extension is in the call. And I can push the function button to connect to whatever extension I have it programmed to. But I want to be able to see when a phone is actually online and registered to sip. 

Presence does not work

When I set the function key to presence, I get none of the above...the led stays off, it does not blink when an incoming call comes in, it does not dial the extension when it push the button. 

I am guessing there is some detail I am missing in this. I originally though my issue was something to do with the PBX not being setup correctly, however my soft phones show presence perfectly. 

  And I've tried 3 different flavors of PBX, elastix 2.6, 3cx, and FreePBX.

Any help would be greatly appreciated!

Thanks