I've installed GPG4WIN on Windows 10 (Build 1511) and had the Problem that my Yubikey 4
(USB smartcard with OpenPGP Applet) doesn't work/react anymore after unplugged the usb
key and plugged it back in. This only could be solved by restarting scdaemon (SCD
I could reproduce this behaviour with GnuPG 2.0.29 (included in GPG4WIN 2.3.0) and the
newest modern version 2.1.9.
I've enabled the debug log for scdaemon and when I plugged the Yubikey scdaemon started
complaining about a stopped service / status change failed.
Even more problematic was the fact that even after unplugging the Smartcard the
scdaemon/gpg-agent was reporting the old (cached) card informations due to the fact that
after unplugging the card status wasn't fully removed in scdaemon.
I've attached the full debug log of my test session. Maybe you can find a place where
something is broken or the scdaemon isn't resetting when the usb smartcard reader is