The checks, in order

1. Is it down for everyone, or just you? Open the site on your phone with Wi-Fi OFF (mobile data). If it loads there, the site is fine — your own connection or its DNS cache is the problem. Wait, or restart your router.
2. What EXACTLY do you see? A suspended page, a blank page, an error number (403/404/500), or "server not found"? Each points somewhere different — note it word for word.
3. Is the domain expired? Client area → Domains → My Domains — check the expiry date. An expired domain takes the site and email down together (see the expiry article in Domains).
4. Is an invoice overdue? Billing → My Invoices — an unpaid invoice suspends the service (the Late Payment article explains the sequence). Paying it is the fix.
5. Did you change DNS recently? Nameserver or record changes need propagation — typically 4–24 hours (see the DNS Propagation guide). Partial weirdness across networks is normal during that window.
6. Did the site break right after a change? A plugin update, a theme change, an edit to .htaccess or wp-config — the last change is the prime suspect; the WordPress white-screen guide covers the classic case.