I got a message from someone that wanted to buy some my stuff that he was trying to do so but was unable too.
He had clicked the button to add it to his cart but then did not know what to do next.
I told him he needed to click on the little shopping cart on the top line to check out and he was happily able complete his transaction.
But.... It occurs to me maybe it is not that obvious, We all know how to use the shop and online shops in general, but maybe a first time user needs something like a prompt when he adds things to the cart to tell him how to check out and this is less a case of stupid user syndrome and more a case of us web-savy people assuming other people know how these things work.