Error message when trying to update software iOS 15.7

What about the check list I provided, everything good there?

If so, try updating using a computer. Also, Apple's servers are getting slammed right now, it may just be overloaded on their end.

Update using your computer -

Update iOS on iPhone - Apple Support

What error?

Can you post a screenshot of the whole screen, it could reveal why you aren't able to update.

Make sure you:

• Are using a WiFi connection (not a hotspot).

• You have an active cell signal (You need both WiFi and cellular service to perform the upgrade).

• Are not using a VPN connection.

• Have your battery charged at least 50%. Better yet, keep it plugged in during the update.

• Do not have power save mode turned on.

• Do not have a beta version installed.

• You have at least 6 gigs of storage available.

You can also check out this article for help -

If your iPhone, iPad or iPod touch won’t update

If your iPhone or iPad won't update – Apple Support (UK)

If you try using a computer to install, it requires less room, 4 gigs should be enough.

On more thing to try, try a forces reset, then try updating again.

Try a forced restart.

• Press and quickly release the volume up button

• Press and quickly release the volume down button

• Press and hold the side button.

• When the Apple logo appears, release the button.

Force restart iPhone - Apple Support (IN)

No I haven't.

What version of iOS are you currently running?

Go to Settings > General > About.

You're welcome, glad you got it sorted out.