All of my Cisco 7960 and 7940 phones have stopped working since I upgraded to 4.211.64-7. I’m running the 32-bit version of the distro. I can make calls with the phones but they do not show as registered in Asterisk and they cannot receive calls. I provision them with the OSS endpoint manager and have never had a problem until now. They download their files just fine and show no status errors but Asterisk still will no longer work with them. Does anyone have any thoughts or similar experiences?
Seems like I always ask the hard questions. 
Try different extension NAT settings.
It’s related to the Asterisk upgrade.
Thanks, changing nat_enable: “0” to nat_enable: “1” in the endpoint manager’s SIP$mac.cnf file for each phone seemed to do the trick.