Why won't my factory unlocked AT&T Note 4 update OTA or via Kies to Lollipop & how can I update it?

[bbmmax]

why won't my factory unlocked AT&T note 4 update OTA or via Kies to Lollipop & how can I update it?

I bought an AT&T version factory unlocked Note 4 a few months ago and it won't update OTA or with Kies or SmarSwitch, to Android Lollipop.
Can someone please help?