Fixing WordPress 404 Errors on Posts and Pages
If your posts show “404 Not Found,” but your homepage works fine, the issue is usually with permalinks.
Go to Settings → Permalinks and simply click “Save Changes.” This regenerates your .htaccess file.
If that doesn’t fix it, manually update .htaccess with default WordPress rules. Also, check that your theme or plugins aren’t interfering with permalinks.
This error can also occur after migrating a site. Make sure your domain and database settings are properly configured.