First, don't panic and don't delete anything. Deletion is one-way; a sign-in problem is not.
Try your other routes. Depending on what you configured, you can sign in by email, with your UIID or .uiid file, or with a login certificate. If you saved backup codes, use them to reset access.
Why biometrics can fail. Sign-in is device-bound and anchored in your device's hardware security module. If you changed device, reset the device, re-enrolled your fingerprint or face, or are using a browser or handset that does not support the underlying standard, the credential on that hardware may no longer match.
After changing device or biometrics, you will need to re-enrol on the new hardware and sign in through one of your other routes first. Your Core ID and aliases come with you — they are not tied to the handset.
Still stuck? Write to [email protected] and include your device, operating system, browser, what you tried and what happened. The more detail, the faster this gets resolved.