Let’s try a couple of things. Get out of the update screen and:
- Open Settings ➔ General ➔ iPhone Storage: Locate the iOS 15 update file here (that is downloaded). Tap on it and then delete it.
- Open Settings ➔ General ➔ About ➔ Available: Ensure that you have at least 6GB - 8GB free space available for the update to download again, verify and install.
- Shut down, ReStart your iPhone and then try updating again. (Read the requirements again in my previous post)
Axel F.