A site that suddenly stops working can have many causes, but they fall into a few groups: the name does not reach the server, the server refuses the request, or the application crashes. This checklist goes through them in the order that finds problems fastest on Plesk.
Before you start
- Note the exact error: a browser message (DNS_PROBE, SSL error), an HTTP code (403, 500, 502, 503) or a Plesk default page.
- Try from another network or your phone's mobile data to rule out a local problem.
Check DNS
- Look up the domain with
dig example.com Aor the IP checker. - Compare the IP with the one in Plesk under Websites & Domains → Hosting & DNS → Hosting (IP address).
- If it differs, fix the record at whichever DNS provider your nameservers point to. See manage DNS records in Plesk.
Expired domains also stop resolving, so check the expiry date with the WHOIS checker.
Check the subscription status
A suspended subscription or domain shows a "suspended" page or 403. In Plesk, look at Subscriptions (administrators and resellers) or the domain overview for a Suspended label. Typical reasons are unpaid invoices, exceeded disk or traffic, or an admin action. Resolve the reason and click Activate.
Check SSL
- NET::ERR_CERT_DATE_INVALID: the certificate expired. Reissue with SSL It!.
- NET::ERR_CERT_COMMON_NAME_INVALID: the certificate does not include this name (often
www). Reissue withwwwticked.
Plesk default page instead of your site
- The files are not in the document root. Compare the folder in the File Manager with Hosting & DNS → Hosting → Document root.
- An
index.htmlplaceholder takes priority overindex.php. Delete the placeholder. - The request hit a different IP on the server, for example IPv6. Check the
AAAArecord.
HTTP error codes
| Code | Where to look |
|---|---|
| 403 | File permissions (644 / 755), .htaccess deny rules, ModSecurity, missing index file |
| 500 | PHP fatal errors and .htaccess syntax in the Log Browser |
| 502 / 504 | PHP-FPM, Node.js or Docker backend down or too slow |
| 503 | PHP-FPM pm.max_children reached, or maintenance mode in the CMS |
Check PHP and the application
- A recent PHP version change can break old code. Switch back in PHP settings to confirm.
- For WordPress, WP Toolkit shows whether maintenance mode is on; disable faulty plugins by renaming their folder in
wp-content/plugins. - Database errors usually mean wrong credentials or a stopped MySQL service.
Check server services (administrators)
Open Tools & Settings → Services Management and make sure Web Server (Apache), Reverse Proxy Server (nginx), PHP-FPM and MySQL/MariaDB are running. Restart any that stopped. Disk full is a frequent hidden cause: check df -h. To rebuild broken web server configuration run plesk repair web.
Next steps
- Read logs in Plesk.
- Tune PHP settings.
- Still stuck? Open a support ticket with the URL, time and error.