I can not get the nightstand option to work I have the iPhone 15 Promax

I have an iPhone 15 Promax and ever since I installed the newest update my nightstand option no longer works. I have my standby mode on in settings, the lock portrait mode off, have my phone on a charger(tried both the MagSafe & USB c) and turn my phone sideways in the dark and nothing happens. I remember trying it a couple weeks ago before the new update and read that under settings I had to also change from portrait mode to landscape mode and it worked perfectly. Now I can’t find that. I think they now say it does it automatically, so did they remove that portrait to landscape mode button in settings and if they did then how do I get it to work and if they didn’t where is it?