Thanks!
My phone is connected by a cable, and I can see my phone as in your screenshot, but not any menu underneath.
I should mention that my phone is iPhone 7 with system 14.6.
Although almost nothing is stored on the phone, but storage information claims the phone is full. It is no longer able to show a breakdown of what is causing it to be full, but it was never the photos etc, only anonymous grey storage.
In my attempt to give space for the apps to work, there is almost nothing in my iCloud account as I moved all my photos into external hard drives. I have only a small number of apps that are active, after offloading data, so I would expect to have about 20 Gb of free storage but have only about 500 Mb out of 32 Mb. I can no longer update apps, or update the system using iTunes.
My hope is that by updating the system from my Mac, I can recover functionality of the phone.