How to sync grocery list changes in Reminders on two iPhones?

hello esteemed colleagues! I created a shared groceries list on the Reminders app and shared it with my wife. Whenever I add something to the list she gets a notification right away, and she can see whatever I just added. However, if she adds anything to the list it only shows to her. I do not get any notifications nor can see what she added. Has anyone been through this?

Mine is a 15 pro and hers is a 14, both running the latest iOS 18.5.

thanks guys!

[Re-Titled by Moderator]