How to Fix iPhone Software Update Failed Error 12.1/12/11 on iPhone iPad
iOS_update_problem_fixes
unable_to_install_update
why_is_my_iOS_update_not_installing?
what_do_you_do_if_your_iPhone_freezes_while_updating?
can_you_stop_an_iOS_update_once_started?
iphone_update_error
how_long_does_iOS_11_take_to_update?

How to Fix iPhone Software Update Failed Error 12.1/...