Hi,
In general, e-commerce solutions are not compatible with cache ; the content is pretty dynamic, specially for the cart and the checkout.
So that's why when you are using some cache extension, we recommend to exclude HikaShop (and HikaMarket) pages from the cache to be sure that you always get the content from the database.
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.