After leaving the car parked over 3 weeks (plugged in, charging 1hr per day), I had the same issue. Rivian asked me to bring the car to service center for appointment 2 months from now (apffff). I followed op instruction and it worked!
My R1S is on 2024.11.02.
Thanks @Polar and @Atlrivian for inspiration on cutting the 2nd row covers. They looked quite professional after installation.
I did leave them down for 2 days to allow for hook and loop adhesion to seats, but that was not enough to keep them up when I lifted the seats. They fell after 2-3...