New Stunning Seaview Apartment with lovely balcony

We booked and paid back in February, but the owner canceled yesterday, Tuesday, just five days before our Friday check-in. Neither the owner nor Booking.com has moved us to accommodation of the same or better standard for these dates, even though that's their obligation. They're both washing their hands of it, and the customer service has been very poor. The owner manages four properties. There's still more than 48 hours to sort this out, but they're doing nothing.