At present, the D80 is a phone that works best with Switchvox or where you’re building your own DPMA (Digium Phone Module for Asterisk) configurations for it. The current version of the Digium Phones Addon for FreePBX - the PHP module for FreePBX that provides a control interface to DPMA - does not do a number of things that the D80 needs.
The D80 needs DPMA 3.3.2 to work at all. DPMA 3.4.0 is better, as it corrects a number of issues with data that it presents to the D80, especially with respect to some of the phone’s applications. Product data sheet notes 3.4 as the minimum requirement.
D80 firmware prior to 1.3.0 doesn’t interact with user+PIN modes. It should interact where global pin is the only auth requirement. You can disable the auth temporarily if you’re running into trouble though.
At present, D80 firmware for use with Asterisk+DPMA is at version 1.3.2. You’ll want to get that version onto your phones.