I also have this problem with my 2012 RX450h. It has sat outside in very cold nordic temps this winter, and I only use it maybe once a week or less, due to working remotely nowadays. The back door used to work from button inside and the key fob until I noticed yesterday (after a loooong time not using the back door) that no matter what I do I can not get the back door to open. Manual button above the license plate does nothing, not one bit of sound. Lock button there works. I would like to get your information also @Herbie if that's not too much trouble. Really looking forward to not having to cough up something north of 1500 euros to the local Lexus shop. I used to take my old RX400h there, and it's somehow always cost an arm and a leg. I figured it's cheaper to get a newer Lexus and it doesn't look like I'm doing it right, lol.
*edit. While waiting for the secret information, I'll get the multimeter out to rule out the battery voltage... I've seen some low batteries in a lot of cars, and from how well this thing operates, I'm assuming the battery will be fine.
