Question: Why is one VoIP stuck as Unregistered?

Background: We have a Cisco UC540 Small Business switch/router/voip combo. This phone was working until I powered everything down to install a larger UPS unit. The phone originally had a status of "Deceased". I removed the registration and tried to add it again. Now it just sits as "Unregistered". I even tried giving it another extension.

I am stuck using the Cisco Communication Assistant since this is small business hardware. There is very limited CLI access. Also, from what I heard, if you access the CLI with out cisco permission, you will void any warranty.

The phone in question is a Cisco SPA501G. It is connected to a SG300-28P. There are 5 other phones on this switch working just fine. I have tried other ports with no luck. Both the link and PoE lights are lit up.

Any ideas?