Unable to download Security Response 16.5.1 (c)

Hey there Scorcher27,

Thanks for visiting the Apple Support Communities. If you're having an issue updating the iPadOS on your iPad, we suggest using the troubleshooting designed to help with update issues found in If your iPhone or iPad won't update - Apple Support.

If you still need some help after that, we suggest getting in touch with Apple Support directly. They'll have the tools and resources needed to further assist with updating your device. You can reach them here: Get Support.

Have a lovely day.

Make sure any VPN software/apps are quit/disabled. You cannot use a smartphone WiFi hotspot either.

You need to do any Apple iOS/iPadOS upgrades/updates using a dedicted wireless, WiFi network that uses a dedicated wireless WiFi MODEM/router box that connects, by hardwired cable, directly to an Internet Service Provider, to access the Internet to do any Apple OS upgrades/updates.

You may need to find outside locations that have free WiFi access that use such a dedicated WiFi network box and service.

Best of Luck to You!

The solution you provided does NOT work for the iPhone 14 Pro. Maybe Apple needs to look into why the update cannot be manually downloaded and installed rather than giving unhelpful advice.