The .htaccess file does not exist on main directory of your site. Modesy has a .htaccess file in the main directory of script files. You should upload this file to your site.
Depending on the operating system you are using, such setting files may be hidden. In this case, you may not see this file.
If you can't see this file, you can create a new file named ".htaccess" in the main directory of your site and you can add these codes to inside this file:
RewriteEngine On
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ index.php?/$1 [L]