Changing address on carte grise

Trying to change the address on our carte grise. Have an ANTS account from when we sold our old car but registered our current one before that, at the sous-prefecture so as I understand it the “code confidential” refers only to the one we sold, yes? So I am trying to get a code and it tells me they will send it by email (wouldn’t that be instant?) and also by post . . . to the address on the carte grise!

The code is not sent instantly. I applied for one recently for someone else & they received the letter with the code a week before I was sent it by email!
I usually get one within 24 hours so it was unusual.

got the code in 2 days recently