Errors when attempting to upgrade from iOS 13.3 to 15.3.1 on iPhone 6s Plus

Assuming you're trying to update your device wirelessly, and bearing in mind that to perform such a procedure you need to connect your device to a reliable and fast Wifi Network with Internet access (no cellular data, unless you use a 5G network, no personal hotspot on your device, no VPN connections are admitted, no Low Power Mode enabled, and I suggest that you keep the device plugged into power during the whole update process), read this support article:--> If your iPhone, iPad or iPod touch won’t update

Also, make sure your device is NOT running a Beta operating system version. Should be this case, you need to remove it before installing any official iOS/iPadOS releases, as per these instructions:--> How to uninstall iOS or iPadOS beta software - Apple Support.

DO NOT forget to create a full backup of your device before updating its operating system, and keep in mind that, depending on the available storage on your device and/or on your wifi network speed, it might take 30-60 minutes to complete the entire update process.

If the issue persists or if the iOS version currently running on your device is very old (from your product list, it seems that the device is still running the prehistoric iOS 13), try to update it via computer (if you don't have a computer borrow one from your friends/neighbors, or ask for help at an Apple Store or Authorized Service Provider), then learn how to update your device manually if you're using a Mac with macOS Catalina or later, or if you're using a Mac with macOS Mojave or earlier or a Windows PC.

If you still get no help, contact Apple Support directly, using this link:--> Get Support

Regards

Giulio

cmichel42 wrote:

Thanks! Upgrading via a hardwire connection to iTunes seems to have solved the problem.

I wish the error message would suggest that instead of just asking me to try again.

I still ran into problems (the upgrade failed halfway through and I eventually wound up resetting to factory setting and then restoring from a backup), but that might have been due to a flakey USB connection?

You're welcome.

Well, flakey USB or unstable/slow Wifi network connection, but it's not that easy to diagnose that problem remotely.

As of now, the phone is on iOS 15.3.1 and working as a phone. Some of the apps need to be re-downloaded, but otherwise looking good.

How can it be running iOS 15.3.1, when (after updating via computer) it should have installed the latest/current 15.6.1 version? No idea about that, unless you used an IPSW file (absolutely NOT recommended).

Some apps might require now iOS versions more recent than 13.3, or, if their developers didn't update their apps, you won't be able to redownload/reinstall those apps.

Regards

Giulio

👍