Exact same problem. Voice attack works just fine with DCS. Viacom pro 2.5 initialized on startup.
I put the Chatter.dll in VoiceAttack\Apps\VAICOMPRO\Extensions
The plugin manager only shows viacom pro 2.5
As the manual says, LCtrl+LAlt+C should bring up the plugin configuration window (keyboard shortcuts are on btw).
However, I cannot get it to open this window and install/register the chatter plugin, and it doesn't appear in the plugin manager either.
@pcwiseman1964 I'm curious as to how you solved this