Most of us use caching plugin to speed up their WP sites, and some use other services like Cloudflare. Cache works perfect for content pages which are static but when it comes to dynamic data along with user sessions, any kind of caching will fail.
Client Area Plugin and Cart & Order Pages, do not support cache as contents are dynamic and fetch live from WHMCS.
While dealing with dynamic data, especially in Ajax environment there are dynamically generated JS some time. So excluding simply URL from the cache will not work and all JS generated by WCAP and WCOP will need to be excluded too.
WHMPress is designed to make sale/content pages and supports cache as long as you are not using currency switcher.