Mine worked for DMW and reserved for the same time every night. I didn't have to do each night separately and got a private table at the time I wanted. I have an "older" phone (2+ years?), Samsung Galaxy A51.
After the last last update everything worked for me. However the port guides don't load. Strangely enough at first, it was the ONLY thing that worked, but now it's gone. Which is fine bc I'm not booking Princess excursions anyway.
Since they want us to prebook everything, I wish there was a way to see each night's menus on the app for each itinerary or ship, even before we step foot on the ship so we can decide if we want to book specialty or not. And then just put an *subject to change without notice if they want to cover their butts. But for the most part, like first night is usually the same, first formal night etc.