Having similar issues with both the site and CC. I was looking to book a stay in Paris, and after entering the location (Paris, France).. I kept receiving a msg 'no properties found'. When I was finally able to get the site to work, and booked a non refundable rate with my cc on file, the next day I got an email msg from the property that my Amex card was rejected and to contact them immediately with a new card or I'd lose my reservation. I called Amex, they told me there was no problem and my card was good. I then called Hyatt who said I had to re-enter my cc info on HGP. I tried doing it, but kept getting a msg that 'card could not be saved' and to use another one. Called Hyatt back, explained the issues, they had Paris Etoile contact me directly and using the same Amex reinstated by reservation.