Settings ->System ->About phone ->Wireless update

Please follow these steps to clear cache before searching for the update again:Settings -> App Notifications ->See all apps ->Show System (top right corner with 3 dots) ->Wireless update-> Clear Data and Cache

Settings ->System ->Reset Options ->Erase all data (factory reset).Power off your phone -> Press and hold the Power and Volume up buttons -> After your phone vibrates, keep holding the buttons for 5 seconds to enter Recovery mode -> Press the Volume up and down buttons to select the option to clear data or restore your device to its factory settings -> then press the Power button to confirm -> Reboot your phone.