Still can't book the Westin in Leipzig on the website due to not having a compatible SPG number. Gave up and went to the Marriott app 5 hours ago and thought I successfully completed a booking and authorized payment at the 87 euro rate. Did not receive a confirmation e-mail and no sign of the booking in the Marriott app or the Marriott website. Also no credit card charge yet as this was a prepaid rate.

Called Marriott. Very helpful agent found the booking after searching, reported it was successfully completed, and explained the issue with the leading "0" on Marriott account numbers not translating over to SPG bookings. He called someone to manually fix my booking, and then it showed on both the app and website.