Never had a problem updating ipad iphone versions in 4 or so years. Ive always done it using itunes and now for some reason im getting a 'corrupted file' message. Tried several attempts and get same problem. So i uninstalled itunes and reinstalled and get the same issue. Itunes running latest version 12.4.3.1, i wonder if there is a problem with that ?
No other settings have changed on router or PC
No other settings have changed on router or PC