Originally Posted by hearingdouble

So I've managed to get to the bottom of this. I think it's to do with how certificates show on the new Marriott system.

I also had a second Cat1-4 certificate, which I have attached to a separate 7-night Cat4 stay (using the certificate in full). This too is showing 45,000 points outstanding on the reservation.

What's actually going on is that my Cat1-4 certificate has a system/cancellation value of 45,000 points. So, the full points cost of the stay is somehow 'reduced' to the value of the certificate, and then the certificate is attached to offset this. I have called both hotels and both are satisfied that there is a certificate covering the full stay. Only, it doesn't look that way on the website!

The trick is to ignore the "My Trips" section of the Marriott website, as this is completely misleading/confusing. Another Marriott IT triumph!