The WooCommerce REST API requires 'pretty' permalinks to work correctly.
WooCommerce POS requires URL rewrites in order to function correctly. This turns ugly URLs into pretty URLs, eg: domain.com/?pos=1 becomes domain.com/pos. If you get a 404 error when trying to view the POS page please enable pretty permalinks by going to WP Admin > Settings > Permalink Settings.
If you have enabled pretty permalinks but are still seeing a 404 error it's possible that your server is not configured correctly for URL rewrites. For information please check the requirements for your server environment. You may need to contact your web host with the above information if your server is not correctly configured.