Misconfigured iPhone settings or network problems are the most common causes of an error during the installation of iOS 15 or later. There have been reports of this issue on iPads as well, so it’s not unique to iPhones.

When you try to install an iOS update on your iPhone or iPad and are met with an error message, this is the cause. A number of incidents occurred while the iPhone was checking the authenticity of the iOS update it had downloaded.

An Error Occurred Installing iOS 15

Method 1: Restart your iPhone in Recovery Mode.

You might not be able to update your iPhone to iOS 15 or later due to a short problem in the iPhone’s modules (like 15.5 currently). In this case, a hard restart of your iPhone may fix the failed update.

However, before moving forward, check to see if the most recent version of iOS is compatible with your iPhone, as not all iPhones can update to iOS 15 or later. While this post focuses on the iPhone, the techniques described here should work just as well on an iPad.

Step 1: You need to quickly press and release the iPhone’s volume up button to increase the volume.

Step 2: To lower the iPhone’s volume, fast push the button and then quickly let go.

Step 3: Then, press and hold the side button on your iPhone.

Step 4: Then, hold the side button until the Apple logo appears (don’t let go of the button when the iPhone’s power menu appears), and then let go.

Step 5: After your iPhone has fully booted up, check to see if it can be updated to the most recent version of iOS.

Method 2: If Your iPhone is Full, Delete Some Apps And Then Redownload the Update.

Since the update cannot be installed if there isn’t enough room on your iPhone, this problem can only arise if storage is running low. Moreover, the update problem can be triggered by a corrupted download.

This issue may be resolved by making more room on your iPhone, erasing the previously downloaded update, then redownloading the update.

Step 1: Launch the iPhone’s Settings application and tap General.

Step 2: Launch iPhone’s storage app and verify that you have more than 10GB of free space. If not, remove unused programmes and erase unnecessary files.

Step 3: Then, in the Storage section of your iPhone’s settings, choose your iOS version and touch on Delete Update to remove the outdated update.

Step 4: The iOS update has been successfully deleted; please restart your iPhone.

Step 5: After your iPhone has rebooted, see if you can successfully install the most recent iOS update.

Method 3: Turn Off The iPhone’s Power Saving Settings.

iPhone’s low power mode limits functionality to the bare minimum by suspending all but the most critical modules and services. The installation of an iOS update will fail if your iPhone is in low power mode, because the modules necessary for the completion of the update are barred from execution.

In this situation, turning off the iPhone’s low battery mode may be the answer to the update’s woes.

Step 1: Select Battery from your iPhone’s Settings menu.

Step 2: To stop Low Power Mode from using any more power, simply turn it off.

Step 3: Next, power down your iPhone, and after it has restarted, check to see if iOS 15 is installed.

Step 4: If it doesn’t work, try charging your iPhone until it’s fully charged and trying again.

Step 5: After it is finished, see if the iOS version on the phone can be updated.

Method 4: Turn Off Your iPhone’s VPN Connection.

Due to the high volume of traffic that a single IP address can handle, Apple’s servers may refuse to validate a connection through a VPN, which could explain why your iPhone is unable to download the latest iOS version. You can try updating to the most recent version of iOS on your iPhone by turning off the VPN on that device.

Step 1: Open General on your iPhone’s Settings.

Step 2: Choose a Virtual Private Network (VPN) or VPN with Device Management now.

Step 3: Once VPN is open, go to the VPN Configurations tab and turn VPN off by toggling the switch.

Step 4: After your iPhone has restarted, check to see if the most recent iOS is available for download.

Method 5: Start Using The App For Constructive Criticism By Logging in.

Failure to sign into the feedback app, which Apple uses to gauge the performance of several OS modules in the beta environment, may prevent you from updating your iPhone’s iOS to version 15 or higher if you are on the beta release channel.

If an error occurred while updating to iOS 15 or later, logging into the feedback app may fix the problem.

Step 1: Initiate the Feedback app and provide it access from your iPhone’s Home screen (if asked to).

Step 2: After you have finished using the Feedback app, you can restart your iPhone.

Step 3: When the iPhone is restarted, see if iOS 15 or later is available for update.