Passkey Authentication

How do I activate and use a Passkey?
Why is the passkey authentication prompt not appearing when I try to log in?
Why does my passkey authentication keep failing during login?
Why is my passkey not being accepted and how do I regain access to my locked account?
Why is my passkey no longer being accepted during login after previously working?
Why am I receiving a "Registration Failed" error when trying to activate my passkey?
Why am I not seeing a prompt when attempting to register a passkey?
Why am I still being prompted to use my passkey after removing it from my device?
Why is the system selecting the wrong passkey when I have multiple passkeys registered?
Why am I not receiving a confirmation message after completing my passkey registration?
Why is the QR code not appearing when I try to use my phone to authenticate?
How can I identify and remove my old passkey after activating a new one?
Can I activate a passkey without installing a third-party app or buying a security key?
How do I transfer my passkey to a new mobile device?
How can I recover my passkey after resetting my phone?