Digium D40 Phone no longer registering

I’m filling in for the person who set this up at a customer’s site and know virtually nothing about Asterisk and Freepbx - here goes. Yesterday all 9 phones in this office were working. They had a problem with their Internet access and we had to reboot the edgemarc SBC. 8 phones came back up fine, 1 did not - Office manager’s phone. I got into FreePBX and looked at connectivity - Digium phones and the extension is listed but the phone information is blank and the presence is blank also. I have restarted the phone connected in her office and now it is connected directly into the Cisco PoE switch. I get a good IP address and when it was in her office she was able to get to the network from her PC plugged into the phone. I have no idea what to look at now. Any help is greatly appreciated.