The blank booking page is nothing new. I've been seeing this for the better part of this year. I do think the issue is some sort of timeout in their javascript client waiting to load the booking records.

When I access from a US computer it hardly ever happens. From my desktop PC at work in Shenzhen I get the blank page about 85% of the time. Sometimes it seems to work better if after sign-in on the main web page, I drop down the menu next to my name that shows the quick MPC account balance. From there is a like to Manage Bookings.

For some reason this seems to work better than using the Manage Booking tab on the main page. Also from the Marco Polo Club account summary page, there is a section labeled 'My Next Flight'. Clicking the 'View/Update' link seems to work better.

But this is just all anecdotal evidence. The fact we all know is that their web site and mobile app are fraught with little frustrations like this.