quick update - I pulled down an old version of a logitech web camera utility - this had a 64 bit driver from 2012 in it. Installed that and it seems to work.
I’d suggest there is still a problem with the way VST connect works with the c920 though - especially as logitech don’t currently make drivers available and the official one bundled with windows 10 64bit doesn’t work.
Seem to remember some issues previously with this camera that were fixed ?