The phone itself is a Mitel model IP480G. My Mitel Connect Director says the Firmware is up to date. If it makes a difference, this is the only IP480G in this building. (Every other phone is IP480.) I have hooked up a different phone in its place, and that one works fine.
Our switch is a ShoreTel ShoreGear 90 (SG90).
We are running Mitel software, and all of our other phones are working just fine. I can access setup information through the Mitel Connect Director, which is running Build:21.90.9738.0, Small Business Edition 100.
If there's more information to get, I don't know where or how to get it off the top of my head, but I'm definitely able to be walked through a way to get more useful information.
Thanks.