I've been using GPG4Win for a long time and I'm always happy to so. :) In the latest version 3.1.13 a problem occured to me though:
I'm using a YubiKey for SSH authentication alongside with PuTTY, the setup is like described here. Now, when I start PuTTY and try to access a remote machine that way, I will get an error: Pageant failed to provide a signature
I can reproduce this reliably every time I use GPG4Win 3.1.13. The problem does not exist with 3.1.12 or 3.1.11. I've also tried PuTTY 0.73 and 0.74, which didn't change anything. (Btw., the rest is a "normal" Windows 10 system.)
It seems that the YubiKey is correctly detected as smartcard (I use gpg --card-status to check this).
The problem is not too bad to me as I can go back to GPG4Win 3.1.12, but there might be more people facing it and one could possibly have a closer look into it. If you give me some directions, I will gladly supply more detailed data, if this helps.
Thank you and keep up the great work!