Your posts/pages still exist; WordPress simply cannot find the rewrite rules to load them.

Common causes:

• Corrupted .htaccess file (most common)
• Wrong permalinks structure
• Server rewrite module disabled
• Plugin forcing redirects
• Incorrect domain or URL settings
• Multisite rewrite issues
• Hosting migration issues

Let’s fix all of them step-by-step.

Steps:

1. Go to Settings → Permalinks
2. Choose any structure temporarily (default)
3. Click Save Changes
4. Select your preferred structure again (Post Name)
5. Click Save Changes again

This automatically regenerates new rewrite rules.

Steps:

1. Go to public_html
2. Find .htaccess
3. Rename it to .htaccess-old
4. Go to Settings → Permalinks
5. Click Save Changes

WordPress will create a clean .htaccess file with correct rewrite rules.

Correct default .htaccess:

# BEGIN WordPress
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]

RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
# END WordPress
    

Ask your hosting support:

• Is mod_rewrite enabled?
• Can they enable the Apache Rewrite module?

If you’re on VPS/cloud hosting, enable it manually:

sudo a2enmod rewrite
sudo systemctl restart apache2
    

This immediately fixes 404 errors for Apache servers.

Check URLs at:

• Settings → General

Both should match exactly:

https://yourdomain.com

Common mistakes:

• Using http instead of https
• www vs non-www mismatch
• Extra slash or subfolder

If locked out of admin, set via wp-config.php:

define('WP_HOME', 'https://yourdomain.com');
define('WP_SITEURL', 'https://yourdomain.com');
    

Plugins that often cause 404 errors:

• Redirect plugins
• Security plugins (Wordfence, AIOS, iThemes)
• Cache plugins creating stale rules
• Migration/clone tools
• Language translation plugins
• Custom post type plugins

Disable all plugins temporarily and test again.

If 404 errors disappear → re-enable plugins one-by-one.

• Folders → 755
• Files → 644

Specially check:

• /public_html/
• /wp-content/
• .htaccess

If permissions are wrong, WordPress cannot update URL rules.

Add this to nginx.conf:

location / {
    try_files $uri $uri/ /index.php?$args;
}
    

Then restart NGINX.

sudo systemctl restart nginx
    

For subdirectory multisite:

RewriteBase /  
RewriteRule ^index\.php$ - [L]
RewriteRule ^([_0-9a-zA-Z-]+/)?(wp-.*) $2 [L]
RewriteRule ^([_0-9a-zA-Z-]+/)?(.*\.php)$ $2 [L]
RewriteRule . index.php [L]
    

For subdomain multisite:

RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteRule . index.php [L]
    

Incorrect multisite rules = instant 404 errors.

Clear/purge:

• WordPress cache
• Browser cache
• Cloudflare cache
• Server cache (LiteSpeed / NGINX)

Then retry opening the URLs.