Why doesn't the app work on my IPhone?

There is a significant difference in Web Push Notifications on IOS/IPadOS. There are limits from Apple regarding Web Push Notification support for iPhone and iOS

Only supports IOS/iPadOS greater than or equal to 16.4

Only recently, Apple has started supporting Web Push Notifications on the latest IOS/iPad OS versions. Accordingly, Web Push Notifications are only supported on devices running OS version ≥ 16.4

How to activate Web Push Notifications on iPhone/ iPad

There are many differences in how to enable Web Push Notification on IOS.
To enable Web Push on iOS, you must add your store to your Home Screen as a mobile app.

Follow these steps:

1. Open your store in Safari/Chrome browser running on iOS 16.4 or later
2. Click on the “Share” button to open the share menu
3. Click on the “Add to Home Screen” option
4. Edit the app name and save the app on your Home Screen

1. Open the app you just added
2. Click allow in the pop-up window
3. Done