Passkeys work in Bitwarden and other password managers
Adding a passkey failed in password managers that save only what they are asked for, such as Bitwarden. They now save one you can sign in with.
Passkeys from password managers. Sign-in never asks for your address first, so it can only use a passkey kept on the authenticator itself. Registration asked for one without requiring it. Phones, laptops and security keys kept one anyway, but password managers that do exactly what they are asked, such as the Bitwarden browser extension, saved a kind sign-in cannot use, and adding the passkey failed. Registration now requires a passkey kept on the authenticator, so these password managers save one you can sign in with.
Left over from a failed try. A passkey from an attempt that failed never reached your account. Delete it from your password manager, then use add a passkey on your account page again.
Docs: passkeys.