Akuvox handsets stopped registering

We have around 130 handsets with around 110 of them being Sangoma and the rest Akuvox. Last friday, all Akuvox’s suddenly failed and won’t register with the Freepbx server.

It’s really odd as the Sangoma’s are still connecting on other sites. I’ve setup a softphone on the site with the Akuvoxs and it works fine which would suggest it isn’t a connectivity issue.

I’ve tried the obvious things of factory reset and adding the details in again (identical to the ones used on the softphone), but they just won’t register. I’ve logged into the handsets themselves, but there is no way to download any form of log file.

Does anyone else have any tips on my next steps?