Sign-in failed
Generic failure: OAuth path returns oauth_sign_in_failed when login is denied by ban after a successful provider link/email match, or the password-login form falls back to this when no clearer API message maps.
Why this happens
Often ban (user or IP) without a more specific public string. Also a catch-all on the login form. Distinct from Invalid email or password (credential mismatch) and Sign-in is currently disabled (site login closed).
Diagnose and fix
1. Member: try again; use forgot-password if unsure of credentials.
2. Admin: check Banned users / IPs for the account or client IP.
3. Confirm Login enabled is on.
4. For social: ensure the linked account is active and not banned.