From what you describe, I think you’re mixing up two things now. Let me summarize it:
You started (in your OP) with Bitwarden’s 2FA options. @grb correctly hinted at the FIDO2-2FA-“passkey” option. This credential can be used as the “second step” when you log in to Bitwarden (usually after you entered your email address and master password – or after using “login with device”).
But when you want to “Log in with passkey” (i.e. only with a login-passkey), then you need to set that up in a different location in the web vault. This is described here: Log In With Passkeys | Bitwarden (PS: on that Help Site, ignore the “unlock” part for now… as you wrote, one problem at a time)
Did you have bluetooth activated on both devices? – Cross-device authentication (CDA) requires that.
Bitwarden’s 2FA-passkeys neither work for “Log in with passkey” nor are they listed as passkeys via (e.g.) the Yubico Authenticator app. - Only Bitwarden’s “login-passkeys” would be…
(BTW, Bitwarden’s login-passkeys on the other hand can’t be used as the second step for logging in… good new is: you can set up both – Bitwarden’s 2FA-“passkeys” and login-passkeys – at the same time with a YubiKey)