Hello, thank you for reaching out to Microsoft Q&A.
Do you remember setting up a passkey on your Windows PC or using your mobile device for your Microsoft account before?
Where exactly are you being asked to enter your passkey? Is it when signing in with your Microsoft account on a website?
If yes, have you tried using your Windows Hello PIN, face, or fingerprint that you use to sign in to Windows? If you have saved passkeys to a synced credential manager like Microsoft Password Manager, your passkey will sync through the cloud and you can sign in using a different device.
To check your passkeys on Windows, go to: Start > Settings > Accounts > Passkeys.
If you have saved passkeys for your accounts, you can remove them from there.