iOS Enterprise distribution error - "cannot connect to server"

I have three iOS enterprise apps on our internet server, and our users have been downloading OTA just fine until today. All of a sudden, I get this message:

Our IT guys have been scrambling to make sure there's nothing wrong with the server. Everything checks out. The .PLIST files and the .IPA files and their locations have not changed.

I updated the iOS in my phone to 8.2, the error is still there.

I remember a while back that Apple decreed that the install files must be served from an SSL directory, which I discovered after a similar problem occurred. We have since fixed that and everything has been hunky-dory until today. Has Apple made some other change like that? I can't find anything on the Apple Developer's page that addresses that. Hoping someone else has been luckier than I.

Thanks.