Can anyone post a list of what should be in:
C:\Program Files\Adobe\Adobe Photoshop CC (64 Bit)\Plug-ins\
On a default install.
That sub directory is completely empty on my install (installed from the cc Desktop Tool), and with all updates in place.
On the PS main menu, under Windows menu item the Windows/extensions item is greyed out and inactive.
Is that normal?
It's normal for the Plug-ins subfolder to be empty, yes. Too many people apparently mixed up 3rd party plug-ins with those supplied by Adobe, which are now supplied in the Required folder (and which should not be disturbed).
Do you have the [ ] Allow Extensions to Connect to the Internet setting disabled in the Plug-Ins preferences panel?