A Safe Troubleshooting Workflow Before Changing Anything Effective troubleshooting starts by preserving the current state, reproducing the symptom, and... How to Isolate a Browser, DNS, Server, or Website Problem A website request passes through several layers, so the same symptom can have very different... What to Record Before Troubleshooting a Website Error Error details are most useful when they capture the exact failing request rather than a general... Diagnosing a Website That Loads for Some People but Not Others If a website works for some visitors but not others, first determine whether the difference... Diagnosing Website Changes That Do Not Appear When an edit is saved but the public page still shows the old version, caching or editing the... A First-Pass Checklist for a Slow Website Slow pages can be caused by application work, database queries, remote services, resource... How to Verify a Fix Without Causing a Second Problem A troubleshooting change is not complete until the original symptom is retested and temporary... Diagnosing an HTTP 403 Forbidden Error An HTTP 403 response means the server understood the request but refuses to fulfill it. On a... Diagnosing an HTTP 404 Not Found Error An HTTP 404 response means the requested resource was not found, or the server is not willing to... Diagnosing an HTTP 500 Internal Server Error An HTTP 500 response indicates that the server encountered an unexpected condition that prevented... Diagnosing an HTTP 502 Bad Gateway Error An HTTP 502 response means a server acting as a gateway or proxy received an invalid response... Diagnosing an HTTP 503 Service Unavailable Error An HTTP 503 response indicates that the server is temporarily unable to handle the request,... Diagnosing an HTTP 504 Gateway Timeout Error An HTTP 504 response means a gateway or proxy did not receive a timely response from an upstream... Diagnosing a Too Many Redirects or Redirect Loop Error A redirect loop occurs when redirects send the browser between URLs without reaching a final... Diagnosing a Blank or Partially Loaded Web Page A blank or incomplete page often means the request started but failed before the application... Diagnosing Missing CSS, JavaScript, or Images If the HTML page loads but styling, scripts, or images do not, inspect the failed asset requests... Diagnosing Website File Permission Errors Linux permissions control which users and processes can read, write, or execute files and... Diagnosing a Website That Is Serving Files From the Wrong Directory If edits do not appear or a domain shows another site’s content, verify the domain’s document... Diagnosing PHP Upload Failures and Size Limits PHP uploads are constrained by several settings. The effective upload limit can be lower than... Diagnosing a PHP Memory Exhausted Error A PHP “Allowed memory size … exhausted” error means the script attempted to allocate more memory... Diagnosing a PHP Maximum Execution Time Error A maximum execution time error occurs when a PHP request exceeds its configured execution-time... Diagnosing a PHP Version Compatibility Problem Applications, plugins, and themes can require a minimum PHP version or fail on a version they do... Diagnosing a Cron Command That Works Manually but Not on Schedule A command can work in an interactive shell but fail under cron because cron runs with a different... Diagnosing Disk Space Problems That Break Website Operations An account near or over quota can fail in ways that do not look like a simple “disk full”... Diagnosing an Application That Cannot Create or Modify Files If an application cannot create cache files, uploads, updates, or generated assets, check both... Diagnosing Large Imports That Fail in the Browser Large imports can hit several independent limits: browser/proxy timeouts, PHP upload size, POST... Reading Resource Faults During Troubleshooting On CloudLinux systems, Resource Usage can show limits and faults for resources such as CPU, entry... Diagnosing a Database “Access Denied” Error A MySQL or MariaDB “Access denied” error usually means the connection credentials or privileges... Diagnosing a Database “Too Many Connections” Error MySQL returns “Too many connections” when all ordinary client connection slots are in use. The... Diagnosing “MySQL Server Has Gone Away” “MySQL server has gone away” can occur when a connection is closed after a timeout, when a client... Diagnosing Database Packet Too Large Errors MySQL rejects a communication packet that exceeds the active max_allowed_packet limit and can... Diagnosing Symptoms of a Damaged Database Table Database-table damage can produce query errors, missing data, or application failures, but those... Diagnosing the WordPress “There Has Been a Critical Error” Message The WordPress critical-error message means a fatal error prevented WordPress from completing the... Diagnosing a WordPress White Screen A blank WordPress page can be caused by PHP or database errors. WordPress documentation lists... Using WordPress Recovery Mode to Isolate a Fatal Error WordPress Recovery Mode is a built-in feature that can activate when a fatal PHP error occurs... Diagnosing a WordPress Plugin Conflict A plugin conflict is most likely when a problem begins immediately after installing, activating,... Diagnosing a WordPress Theme Conflict A theme can cause fatal errors, blank pages, layout failures, or missing functionality when its... Clearing WordPress After It Is Stuck in Maintenance Mode During an update, WordPress creates a .maintenance file in the WordPress root directory. If an... Diagnosing WordPress Permalink 404 Errors If the WordPress home page works but posts or custom routes return 404, the rewrite rules used by... Diagnosing WordPress Changes That Still Show the Old Version WordPress itself does not include a general page cache by default, but browser cache, cache... Diagnosing a WordPress Core, Plugin, or Theme Update Failure WordPress updates can fail because of filesystem ownership/permissions, insufficient disk space,... Using WordPress Debug Logging Without Exposing Errors to Visitors WordPress provides WP_DEBUG, WP_DEBUG_LOG, and WP_DEBUG_DISPLAY for debugging. On a public site,... Diagnosing a WordPress Admin Area You Cannot Access If the public site or wp-admin fails after a plugin/theme change, use the least destructive path... Diagnosing a Domain That Works by IP but Not by Name If the server responds by IP address but the domain name does not reach it, focus on DNS and... Diagnosing Intermittent or Conflicting DNS Answers Different DNS answers can occur when authoritative nameservers do not contain matching zone data... Diagnosing DNS After Changing a Domain’s Nameservers Changing nameservers changes which DNS servers are authoritative for the domain. The new... Diagnosing DNSSEC After a Registrar, Nameserver, or Server Change DNSSEC validation depends on the DNSKEY information served by the authoritative DNS system... Diagnosing HTTPS That Works on One Hostname but Not Another An SSL certificate is valid only for the hostnames included in its certificate names. A... Diagnosing AutoSSL When a Domain Does Not Resolve Correctly AutoSSL domain-control validation depends on the domain being reachable and correctly delegated.... Diagnosing a Force HTTPS Redirect Option That Is Unavailable cPanel’s Domains interface can force HTTP requests to HTTPS, but the option is available only... Diagnosing Email Delivery with cPanel Track Delivery cPanel Track Delivery displays delivery reports for messages handled by the account and can help... Diagnosing a Mailbox That Cannot Receive New Messages A mailbox that reaches its assigned storage quota cannot receive additional mail. Account-wide... Diagnosing SPF, DKIM, DMARC, or PTR Warnings in Email Deliverability cPanel Email Deliverability checks mail-related DNS records that receiving systems use to... Diagnosing an Email Client That Cannot Connect Mail-client connection problems are often caused by using the wrong server name, port, encryption... Diagnosing FTP Connections That Stall or Time Out FTP uses separate command and data connections. A login can succeed while directory listings or...