When the game is launched in a 64 bit instance it will never attempt to grab the microphone stream from the computer making VON impossible, the only way I found to fix this issue after trying:
I've tried all my mic ports, checking the default in steam, trying just my mic no headphone (as I have a 2-1 splitter), ive tried reinstalling, running steam and arma3 as admin, no mods loaded, launching game and joining through in game browser and not the launcher, a whole different headset, changing and checking keybinds, deleting arma3 files in the appdata folders, checking mic perms, profiling build, opening the port for steam von and p2p, creating a new windows profile, removing all audio altaring programs (e.g. voicemod, thx spatial), deleting microphone perms in regedit

Is to switch the game to 32bit mode, however this presents me with multiple crashes during gameplay from which I can only presume is memory related?