When using a Yubikey as a GPG card, entering the wrong PIN multiple times will result in a disabled state. You can unblock the Yubikey by using the admin PIN.
$ gpg --edit-card gpg/card> admin Admin commands are allowed gpg/card> passwd gpg: OpenPGP card no. D2760001240102010006096610530000 detected 1 - change PIN 2 - unblock PIN 3 - change Admin PIN 4 - set the Reset Code Q - quit Your selection? 2