Trixbox to FreePBX password problems

We’ve got an office running Trixbox (Asterisk that we’re trying to move to FreePBX Trixbox is a physical server at the remote office. FreePBX is a virtual here at my office. The FreePBX setup is a fresh build (not trying to update Trixbox into FreePBX). Once we’ve moved them over to the virtual, we’ll take their existing physical server and replace all of the spinning parts, then load the virtual back onto it. When this is all done, they’ll have a new physical FreePBX system.

With all of that info out of the way…when we attempted to cut them over from the physical to the virtual, we couldn’t get the existing phones to register on the new system. The phones were online (you could access the WebUI, etc), however, they were constantly throwing 403 or 408 errors. The only variation between the 2 systems was a different secret (Trix - password, FreePBX - password1). I modified the FreePBX extensions to have password instead of password1, but it still wouldn’t register the phone. We also tried to factory default and erase local configs on the phone, hoping that a fresh phone would just grab the info and go, however, we got the same results as before. What am I missing to get these phones onto the new system?

Phone - Aastra 6755i
Firmware Version:
Firmware Release Code: SIP
Boot Version:
Date/Time: Feb 22 2011 22:17:14

I was able to get the phones to register. In Global SIP settings, under Basic SIP Authentication Settings, I changed the password on the phone to password1 (the password on the FreePBX side), then restarted each phone. The phones registered successfully on the new system.