Added .html to Woocommerce permalink but pagination don’t work!

Adding .html won’t do anything for SEO’s sake – in fact, it will more likely cause problems than anything else. WordPress (and therefore WooCommerce) don’t use HTML files to display – it’s PHP files, which is why if you go to a page like the login, by default it’s something like example.com/wp-login.php. Out of the hundreds or thousands of WordPress sites I’ve worked with in my time working for WooCommerce, none of them needed to add .html to a page for any reason, so I would highly suggest against it.