2024 iPad Pro activation is failing

I am trying to activate a new M4 iPad Pro, to replace my old iPad. The activation fails upon the step to update the new iPad to iPadOS 18.1. I have a Software Update dialog box on the new iPad Pro, and my old iPad is sitting alongside with a dialog box "Waiting for Software Update". Both new and old iPad just have spinning wheels on this step. The new iPad Pro did request, download and prepare the 18.1 update as far as I can tell, the failure is occurring at the start of the install.