Won’t get past “ verifying update”

I had the same problem and it’s because I didn’t have the 6GB required for the install. I had 4GB available, which was enough to download but not enough to install. Once I deleted 2GB of data, I passed the verifying update screen

Kind of a Catch 22.

You cannot update unless cell service is working on the phone at the time. Contact your carrier to get cell service working again, then you can update to iOS 17.2.1