A message showing”There is an error while installing iOS 15.6.1. Try later?

See -> If you can't connect to the App Store, iTunes Store, or other Apple services

If you can't connect to the App Store, iTunes Store, or other Apple services - Apple Support

Check iPhone type & iOS version -> Go to: Settings -> General -> About.

If your iPhone is eligible for an update, you can check by reading this Apple article:

iPhone models compatible with iOS 15.6.1

iPhone models compatible with iOS 15.5 – Apple Support (UK)

Then go to: Settings -> General -> Software Update

See the following Apple articles:

Update your iPhone, iPad, or iPod touch

Update your iPhone, iPad, or iPod touch - Apple Support (IN)

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

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

You can do the update via PC, see this Apple article: Update software on iPhone, iPad or iPod touch in iTunes on PC

Update software on iPhone, iPad or iPod touch in iTunes on PC – Apple Support (UK)

If you have a Mac see this Apple article: Update your iPhone, iPad, or iPod touch with the Finder

Update your iPhone, iPad, or iPod touch with the Finder - Apple Support

You need about 6 GB device storage and good Service & Wi-Fi.

If they are On, turn Off Hotspot & VPN.

Click here for more support and assistance.