Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
What device are you trying to log on to WordPress with? a Windows PC, an Apple computer, or a handheld (Android, iDevice, etc.) ?
Are you logging in as usual? and have you logged in before on this device, to WordPress?
If you are on a handheld device, and have not logged in to WordPress on that device before, it may be that the PIN prompt is for some other function than WordPress, such as initiating a Bluetooth connection (which usually requires a PIN), etc.
Let me know. And be it suggested, that the PIN might be a default, such as