Note that if you’re using a simple server such as “http-server” or even something like “wamp”
without any configuration, the problem is normal.
Indeed, when you access the homepage, your “index.html” is automatically loaded, but if you access something like “http://url/part1”, the server will look for a folder “part1” that contains an “index.html”
page => error 404.

So you have to make sure base url like this /

and Make a htaccess file with code

<IfModule mod_rewrite.c>
   RewriteEngine On
   RewriteBase /
   RewriteRule ^index.html$ - [L]
   RewriteCond %{REQUEST_FILENAME} !-f
   RewriteCond %{REQUEST_FILENAME} !-d
   RewriteRule . /index.html [L]
</IfModule>