OK, this was a result of the Debian 8 Linux on our system failing to automatically update the 3CX Phone system, resulting in a total failure of the phone switch. It seems that the Debian Linux community moved some critical file repositories, resulting in 3CX's switch update script failing during a Debian component refresh that precedes the 3CX update itself, leaving the phone switch dead and eventually timing out the license. Yeek. I have learned a lot more than I ever wanted to about Debian Linux :-) The switch is back online, our phones are working, but I still have an OS upgrade from Debian 8 to Debian 9 to do, and there are more Debian 8 repositories that were moved, preventing that. The 3CX community has been extremely helpful. Since the tech support load here on the COmm Center has been mercifully light so far (after getting through the backlog from being away at NEAIC/NEAF), I'm just going to keep going till I have it all in good shape. This VoIP phone switch system ran totally maintenance free for almost three years so I'm not complaining. Thank heaven I kept detailed log of my process of installation and configuration, and I take weekly backups of it all -> my Google Drive.