Just to let folks know that I was encountering this issue tonight and know others have too...
When they have selected their pre-order and any extras they get forwarded --- to the original page
The thing that worked for me was --- use a different browser.
It is presumably either the browser (Firefox failed, while Chrome worked) or the settings but I couldn't see where the settings were causing an issue ( and am computer-knowledgable enough to understand most of the time ).
Anyway thought I'd add this as I've seen posts in other threads (on other forums) related to this and found out THIS is the correct forum for posts related to such issues (forgive me if this is mistaken on my part).