Could not complete sign-in
Social login reached the site callback but could not finish creating a session (or hit a callback rate limit / unexpected gate). Shown via ?oauth_error= on login/register.
Why this happens
Generic OAuth finalize failure — not specifically a bad client secret (that is often Could not complete sign-in with the provider). Country-confirm link failures use the “Try again” sibling.
Diagnose and fix
1. Retry social login once; try another browser if cookies are blocked.
2. Admin: Social login mod on; provider credentials correct; check app logs at callback time.
3. Confirm OAuth redirect URI matches the provider console and PUBLIC_APP_URL.
4. If the account is pending/banned, expect those specific messages instead.