adolphe50 Said:
"Update to IOS 15.7.2: I tried to update it from iTunes but still. There’s always an error when downloading. It looks like it finally finish download but instead of installing, it brings out an error message."
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Troubleshooting "Update Using a Computer"
I. Provide Two Things:
A. What is the Error Message?
A screenshot of the message would most certainly help. IMPORTANT: Leave of personal info, by covering it with red rectangles through use of the Photos app. Go Here: Take a Screenshot on your Mac - Apple Support
B. What's the Operating System?
If using a Mac, note that iTunes was discontinued in macOS Catalina. The TV app is for movies and TV shows, whereas the Music app is for music. Go here: What Happened to iTunes? - Apple Support
II. Performing the Update
A. Use a New Computer:
Try using a different computer to perform this update. Use a friend or family member's computer (with their permission, of course).
B. Boot in Safe Mode:
Try performing this in Safe Mode. See if it all now works. In Safe Mode, only necessary items load (i.e. the caches), and new preferences are set aside. Go Here: Start Up your Mac in Safe Mode - Apple Support
C. Create a New Administrator:
Create a new Administrator, seeing if you can then perform this. Go Here: How to Create a New Administrator Account on Mac OS - OSXDaily