iOS 18.5 is downloaded, but it keeps saying it’s temporarily unavailable to verify update for installation

Perhaps a long shot:

Do you have a 3rd party VPN installed, even if you are not using it? If so, delete the VPN profile in Settings/General/VPN & Device Management/VPN. Don't just turn it off; delete the profile. If that fixes it, you can try reinstalling VPN. 

iwu213 wrote:

are you for real, and what iPhone do you use?

I am for real; a large percentage of connectivity problems, especially after an iOS update, are caused by incompatibility between a VPN profile and the iOS networking subsystem; when installed a VPN configures itself to the hardware and current iOS version. Unable to verify is either a network problem or an Apple download server problem. As→Apple - Support - System Status shows no current problems, the issue is either with your iPhone’s networking or a problem with your Wi-Fi router if that is what you are using or with your cellular network connection if you are using that.

Hello~ Are you running beta? How’s the storage space on your device? Strong WiFi ? I don’t see that you are connected. Also you may need to charge your iPhone a bit more if it’s under 50%. Yes…before you ask I am for real…

~Katana-San~