I have a Yubikey 4. On a Windows 7 64 bit machine I installed Gpg4Win which includes GnugPG. I was able to successfully import public keys. I plugged in the Yubikey 4 and Windows correctly identified and installed the proper drivers.
However, issuing the ' gpg --card-status ' command results in:
gpg: selecting openpgp failed: No such device
gpg: OpenPGP card not available: No such device
This is strange behavior as I can see the Yubikey information using the Yubikey Personalization Tools (name, serial number, etc).
I have confirmed in Windows Services that "Smart Card" service is running. I have also ran 'scdaemon.exe --server -v' and it says "smartcard server ready" and I also tried "gpg-agent --server -v" and it says "OK Pleased to meet you". When I run the gpg --card-status command it doesn't reflect any verbose in those command prompts.
Any ideas on what would be causing this? Yubikey personalization tools and neo manager can detect and read the Yubikey but GPG cannot.
EDIT: I did the same steps on a different Windows 7 64 bit machine and it works (download gpg4win, import public keys, insert Yubikey and type in gpg --card-status and it loads stubs. So this seems to be a local issue on the local machine, so what services or what tools exist to diagnose the issue on the original machine where it doesn't read the card (but Windows does). I also tried opensc and it detects the Yubikey as well, but gpg does not.