Hi iPPbeginner,
Welcome to Apple Support Communities, and congratulations on your awesome new iPad Pro. Rest assured, we're committed to helping sort out this issue with your widget stacks.
To start, let us know if you've had a chance to restart your device since noticing this behavior. If not, please do so now. Here's a guide with the recommended steps to restart:
Restart your iPad - Apple Support
It may take some time to determine if the Smart Rotate feature is working at that point. We recommend monitoring for a day or so. If it doesn't start working at that point, let us know what happens if you completely delete a widget stack, then recreate it.
We'd like to share the following guide with more information:
Use widgets on your iPad - Apple Support
Let us know if you have any questions.
Have a great day!