In my case it was related to another issue of this plugin.
https://ww.wp.xz.cn/support/topic/duplicate-entry-in-errorlog/
After solving that issue, this one was solved too.
I was having this exact issue and I fixed it by
ALTER TABLE wpprefix_phplugins_cart_contents DROP PRIMARY KEY;
I installed the plugin normally from the Plugins page inside the admin panel so I don’t understand how the primary key was set in the first place if it’s not intended. In my case, after solving this issue, it also solved https://ww.wp.xz.cn/support/topic/shows-only-first-added-item/
This issue also happens to me. The Cart Value amount is correct at all times but it only shows the first item added. If a user removes it and adds a new item, it’s not updated in the cart details in the admin panel. It keeps showing the first item added only.
