Shopping Cart and Membership issue

Hello WPMU Dev Support,

On I have been testing the shopping cart functionality in conjuction with GridMarket Theme.

When I add something to the cart via one og the Add Cart buttons the following:

1) It seems to be added to the cart but the number of items in the header remains zero

2) As I add more items the header total is not correct and at times shows zero

3) When I view the shopping cart from the header it shows all items added

4) When I use the menu Store -> Shopping Cart it only comes up if the item total in the header is greater than zero, also it does not show all the items that should be in the shopping cart

i.e. Though I have added 4 items to the shopping cart the header only shows 1 and the Shopping Cart page will only show one

Also, I do not want anyone proceeding to checkout without having logged in or registered first.

Really hoping this is something simple and I have missed setting something up.

Can you please advise.

Kind regards,