Cannot Checkout

Hi,

This looks like a SEF issue.
First thing I would recommend is to update your HikaShop and see if that helps.
If not, could you provide a screenshot of the settings under the Checkout tab of the HikaShop configuration and more precisely of the "force menu on checkout" setting ?
I suppose that you have selected the "checkout" menu item from your main menu. Could you provide screenshots of the settings of that menu item ?
Also, under the "Features" tab of the HikaShop configuration, you have a SEF section. There, there is a setting "Checkout SEF name". This might be in conflict with the menu item alias being "checkout" since this usually defines the controller in the URL of the checkout. What do you have in that setting ?