iPhone not updating

For the update, see the articles below.

Get help with over-the-air iOS updates  -

Update – Can’t or can’t restore   -

Have you tried using iTunes on a computer or Finder if running Catalina or later to do the update?

Update software on iOS devices in iTunes on Mac. -

Phone, iPad, or iPod touch - Update with Finder.  *

iPhone, iPad, or iPod touch - Update with iTunes.  *

If you see an error when you update or restore your iPhone, iPad, or iPod    *

Updating iOS: common issues and solutions.  -

If you can't update wirelessly, try to update by using a computer, as described in this article:

Update your iPhone or iPad - Apple Support

Your iPhone 7 can only be upgraded to iOS 15.7.1