If the force restart didn’t help you fix the iPhone frozen during update issue, you may restore your iPhone in Recovery Mode. Update or Restore iPhone in Recovery Mode Hold down the Home button and the Power button at the same time > Release both buttons when the Apple logo appears.
If you see an updating message, then it means that the update is still in progress. To check whether the update is stuck, you can press any button. You can connect your device to a power source and wait. The progress bar might be moving very slowly or seem like it isn't moving.
How to Fix iPhone Frozen During iOS 15 Update A corrupted app or system error should also be blamed when iPhone stuck on Apple logo with loading bar.In this case, the firmware will not download normally so your device gets stuck. When the Wi-Fi is not stable, your device may freeze during the update. Insufficient memory can affect device performance and cause unpredictable behavior, including freezing. Various reasons can cause this iPhone frozen during update error and the following are the common ones. However, if the progress bar on your iPhone screen hasn't moved for at least one hour, it is very likely that your device gets stuck. If your device contains a large number of data, the process can take up to an hour. The fact is that the iOS update will take longer than your expectations. When updating iPhone or iPad, a progress bar will show you the installation progress. The Issue: iPhone iPad Frozen During Update