The "Error 404 - Page Not Found" in WordPress occurs when the server cannot find the requested page. This can happen for several reasons. Here are steps you can take to address this issue:

1. Check Permalink Settings:

   • Go to your WordPress dashboard, navigate to Settings > Permalinks, and make sure your permalink structure is set correctly. If it's not, choose a different structure and save changes.

2. Flush Rewrite Rules:

   • Sometimes, the rewrite rules in WordPress can become corrupted. To fix this, go to Settings > Permalinks and simply click "Save Changes" without making any changes. This will flush and regenerate the rewrite rules.

3. Check .htaccess File:

   • If you're using Apache, make sure your .htaccess file (located in the root directory of your WordPress installation) is correctly configured. If it's missing or contains incorrect rules, it can cause 404 errors.

4. Check for Typos in URLs:

   • Ensure that the URLs you're trying to access are correct and don't contain any typos or misspellings.

5. Check for Broken Links:

   • It's possible that the link you're trying to access is actually broken. Use a broken link checker plugin or a tool like Google Search Console to identify and fix broken links.

6. Check for Page/Post Existence:

   • Verify that the page or post you're trying to access actually exists in your WordPress dashboard. If it's been deleted or not published, it will result in a 404 error.

7. Review Theme Files:

   • Check if your theme has a custom 404.php file. If it does, review the code to ensure it's not causing the issue.

8. Check for Plugin Conflicts:

   • Deactivate all plugins and see if the 404 error persists. If it disappears, reactivate each plugin one by one to identify the conflicting one.

9. Check Server Configuration:

   • Contact your hosting provider to ensure there are no server-level restrictions or configurations that might be causing the 404 error.

10. Inspect Server Logs:

    • Review your server's error logs for any specific information about the 404 error. This can provide more context on what's causing the issue.

11. Use a Default Theme:

    • Temporarily switch to a default WordPress theme (like Twenty Twenty-One) to see if the issue is related to your current theme.

12. Recreate the Page/Post:

    • If none of the above steps work, try recreating the page or post with a new URL slug.

Remember to always back up your site before making significant changes. This allows you to revert back if any further issues arise.