Plugin Failures "Installation of --- Failed". Error

[Ed Schreibman]

In V 6.91. I get “Installation of — Failed” error on any plugin install/update attampt.
Steps taken:
Uninstall / Clean Install (including Program Data).
Ensure “Plugins in user’s AppData directory are enabled.”
Ensure Firewall not blocking.

Win 10, 64 bit

ANy assistance appreciated.