Software update button is not responding on my iPhone

Hello again!

The iPhone should default to upgrade to next supported iOS, when

set & does automatically; but there are occasions where it may not.

The Settings in iPhone should sustain the update cycle.

Update your iPhone or iPad - Apple Support

//support.apple.com/en-us/118575

This article covers most details on updating iOS.

There is no longer a version iOS 14.x and so Apple (a few years ago)

allowed version iOS 15.8.x to support several models directly there.

Your iPhone 7Plus, first SE, and others to use same iOS 15.8.x update.

And there is a way to update the iOS by cable with Computer, or WiFi..

The charge USB cable can be used between a PC or Mac to update.

This is the support article for problematic update/upgrades.

If your iPhone or iPad won't update - Apple Support

//support.apple.com/en-us/108905

The Earlier linked Article covers 'Automatic Updates' too.

Your iPhone should be capable of download & install an

update by itself, if provided power and wi-fi; overnight.

jeanard224 (Author)

Perhaps your model of iPhone has no updates available?

Helps to know more about the hardware involved too.

Then some idea could be exposed & reasons revealed.

Identify your iPhone model - Apple Support

jeanard224 (Author)

Following List of iPhone models (wikipedia) shows iOS step

updates of inclusion and later supported versions of each.

• List of iPhone Models - Wikipedia

https://en.wikipedia.org/wiki/List_of_iPhone_models

When where if the product cannot be used, refer to a local

'Apple Authorized Service Provider' or Official Apple Store.

•Genius Bar Reservation and Apple Support Options - Apple

//www.apple.com/retail/geniusbar/

Get Software &/or Hardware Help from links within this article.

In reference: Apple product support staff are 'Genius' personnel)

For inspection of devices are walk-in, repairs require appointment.

How to put your iPhone in diagnostics mode - Apple Support

How to run an iPhone diagnostic? - California Learning Resource Network

Maybe your iPhone doesn’t support the update for example someone with iPhone 6 can’t install iOS 18.0