Cart does not work as a guest

In looking at your site, it may be your caching plugin. While Sunshine tries to tell all caching plugins not to cache it’s pages, the plugin you are using may be ignoring it. I recommend seeing if your cache plugin allows you to set exclusion rules and block all caching on Sunshine related pages.

Indeed It is the fault of the cache plugin.
I have excluded all the pages (it does not allow me to select) and now it works.
Could this bug be fixed in the future? I use “WP fastest cache”
Thank you very much for the solution.

I use this same cache plugin and everything works as intended.

This isn’t really a “bug” in Sunshine. I am not quite sure why your install of WP Fastest Cache is not recognizing Sunshine’s attempts to tell it to not cache it’s related pages. WordPress allows plugins like Sunshine to define a variable called DONOTCACHEPAGE and all cache plugins are supposed to acknowledge this request. It seems to work for almost everyone, on rare occasion like you it wasn’t for some reason. With the cache exclusion rules in place you should be all set.