New iPhone 12 Pro won't get past "Confirm your phone number".

Doing the typically simple task of migrating from iPhone 11 Pro to iPhone 12 Pro. I put the phones side-by-side, scan the animated star thing with success, and soon get to a screen to "Confirm your phone number." The number is correct. The only action on the screen is to click Next. But when I click Next, nothing happens. I can just keep touching Next to no avail. I've restarted both phones and the process a few times and nothing changes. Maybe if I choose to set it up manually, I will have a different behavior, but probably not. Any ideas why clicking Next does nothing here?