Why doesn't my AT&T Lumia 635 see the Denim Update?

[WPCentral Question]

I have a Lumia 635 on the regular (postpaid) AT&T network. It is stuck on a pre-Denim version. I ask it to check for updates, but it swears that no further update is available. Yet Microsoft's page claims that the AT&T Lumia 635 should update to Denim.
I see no way to force an update. (Microsoft's page specifically says that offline update is not possible.)

 

[ashram]

Tried Windows Device Recovery Tool??

plug in your phone and it'll tell you if you are on the latest available or not.... only downside? it's essentially a hard reset.