this has happened twice so far over the last 1000km. Basically I would use cruise control several times and then it won't accept my new "set". The radar says ready and active but no matter what I press I can't get it to take the speed. Only turning the car on and off fixes it. I have a 2023 is500.

 

I also have a 2023 IS 500 and haven't seen such an issue.

Have you tried using "resume" instead of "set" again? Have you tried simply turning cruise control off and on again using the button on the end of the stalk?

If you have tried these things, it may be good to take to the dealer. It's under warranty, after all.

 

Cruise controll don’t work while driving manual mode. This happened to me while driving at a highway had it on manual mode and couldn’t figure why my cruise controll won’t set. Just to find out it only works while your at automatic mode

 

maybe it was on manual. I guess I could kind of see that but I feel like I'd notice. I tried resume set everything.

 

I figured it out. Not exactly manual mode but when I down shifted twice it wouldn’t engage cruise until I upshifted. Even after waiting a few seconds.

 

any chance there's metal-based protective-coating residue / film or debris on your front "L" logo?
make sure it's not hit / dented-in / removed / dislodged.

93yo neighbor reversed onto the "T" of my old Toyota Camry & there's no obvious damage until I tried to activate Adaptive Cruise Control, which won't turn on.
realized the "T" is dented-in (pushed-in).
freaking MiddleField Road workshop in Mountain View, CA which is GEICO insurance official repairer, replaced the sensor with a fake none-OEM.
I decided to total the car after the repair & get $$$ to buy a new Lexus IS