why can’t I Download Google app of iOS 15.0 when I already downloaded up to iOS 15.8 on iPhone 7 Plus

Adeyemi3565 wrote:

https://discussions.apple.com/content/attachment/55f6fef7-e518-47ab-9ffa-0a9b46836356

And that is why you can't download the Google App. Your iPhone is NOT updated to iOS 15. Until you update your iPhone to the current version iOS 15.8.2, you will not be able to download the Google App.

Since you've skipped a lot of iOS updates since your current iOS 14.3, you may need to use a computer to update your phone. See how here --> Update your iPhone or iPad - Apple Support

Connect to a WiFi network.

Connect to the charge circuit.

Turn off the Low Power mode option.

Please see: Update your iPhone, iPad, or iPod touch - Apple Support

And: If your iPhone, iPad, or iPod touch won't update - Apple Support If the above Apple articles do not help, please post back with relevant information. 

Because the phone your are trying to install it on is running a lower version than iOS 15.

What version of iOS are you running on it? Please post a screenshot of the version.

Tap Settings > General > About > iOS Version.

What iOS Version is currently installed on your phone?

Note.....you will not be able to update your phone unless you have a good Wi-Fi connection and Low Power Mode is turned off.