hi I just saw this topic and I had similar situation not sure if it will work for you but I used this plugin but to solve the problem it adds code to the site url like /?c=04007ae3e449
it has a setting in advanced Currency switching with page caching support
If you are using a static caching plugin, currency switching may not be working properly. Enabling this feature appends additional query string at the end of the URL (depending on the active currency), which causes cache invalidation.
https://codecanyon.net/item/woocommerce-ultimate-multi-currency-suite/11997014?ref=Dev49net
and the plugin author replied about this issue, see below
Thanks for the purchase!
1. Unfortunately, that is not possible. The appended parameter solution is the same one that WooCommerce uses for Geolocation with page caching, take a look – https://woocommerce.wordpress.com/2015/07/02/making-geolocation-static-cache-friendly-in-2-4/ WooCommerce adds ?v=XXXXX parameter, and my plugin adds ?c=XXXXX parameter.
When pages are cached, PHP basically does not run. So based on the URL, a caching plugin loads a statically saved HTML file of the page. The problem is that each product can have different prices/currencies under the same URL. That’s why URLs need to be differentiated, so the additional parameter must be added.
If you are using a cache plugin, such as W3TC, this parameter is necessary in order to use multi-currency functionality. For multi currency sites, the typical cache plugin rule “same URL = same content” does not apply, so the URLs need to be differentiated. I decided to go with WooCommerce AJAX geolocation feature, since it was already tested and proven to be working.
Please consider doing some tests whether you really need a caching plugin in the first place. From my experience, when running a reliable hosting without having WordPress bloated with plugins, the benefits of using a caching plugin are very little.
