1. Log in to the WordPress Dashboard.
  2. In the navigation menu click Settings, then click Permalinks.
    You will then be on the WordPress Permalinks Settings page.
  3. Notice what setting you have selected, options are Plain, Day and name, Month and name, Numeric, Post name, Custom Structure. If you are using a Custom Structure copy and save it, so you can put it back later.
  4. Select the Plain setting, then click the Save Changes button. If you already have the Plain setting selected, choose Day and name, then click the Save Changes button.

    You will then see a message stating Permalink structure updated.
  5. Now, select your original setting, and click the Save Changes button again. You are finished when you see the “Permalink structure updated” message again. Your site permalinks should now be working again.

    You may have to clear your browser cache before testing in order to see the change.

I am unable to log in to WordPress

If you are unable to log in to WordPress to make the above changes, you can reset your .htaccess file manually by replacing the contents of the file in the public_html directory, with the following...

# BEGIN WordPress

RewriteEngine On
RewriteRule .* - [E=HTTP_AUTHORIZATION:%{HTTP:Authorization}]
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]

# END WordPress