We recently moved our website to a new server. Unfortunately, some people who visited our site while we had it hosted on a previous server may now experience some difficulty when they visit us again (now on the new server). This is related to the 'cookies' - very small files that help the website to remember things such as what items you have added to your cart, and that you have logged in.
You need to clear your 'cookies' from your browser.
This article here gives instructions on how to do this in most common desktop and mobile browsers: