In this instance, it's conceivable that the network or update server is now unavailable. To upgrade with iTunes, you'll need a computer with the most recent version of the operating system and the most recent version of the iTunes program installed. After you've gathered all of your materials, you can go on to the next steps:

• Connect your iPhone SE to your computer with the USB or Lightning connector that came with it.
• On your PC, launch iTunes.
  • Then go to iTunes devices and find your iPhone SE.
  • Select the Summary tab.
  • Select Download and Update from the drop-down menu.
  • Enter your passcode if prompted.
  • Wait until the update has finished downloading and installing on your device.