Just to resolve this: I did a reinstall of Windows 10 and my issue seems to be fixed. I guess what was said earlier regarding some driver-related files was messing with my audio, even though I hadn't upgraded my OS.

I've noticed other people from this forum and on other social media have a similar problem, even with many hours in the game without issue, then they suddenly & recently lose access to voip like this. As a relatively new player, I don't have the countless hours in DayZ to speak for this, but could this have been broken for certain players in a recent update?

Hey, thanks for replying.
I installed Windows 10 directly when I built this PC, so it was a clean installation. I've never had a previous version of the OS, just Win10.