Update Apple Watch

I have an iPhone 12 Pro and Apple Watch 4. Watch OS 7.0.2. Available memory in the watch is 10.3GB.

I keep getting the following message when I try to up date Watch OS. "The watchOS update couldn't be verified because you are not connected to the internet"

• Both the phone and watch are connected to the same wi-fi network.
• Watch is always on the charger. Phone is beside it and fully charges.
• Tried updating the OS using the watch, and get the above message.
• Tried updating watchOS using the iPhone and get the above message.
• Deleted apps on the watch, and still no joy. In case anything was interfering with the process.
• De-coupled (if that's the correct word) the watch from the phone, and then reconnected, and got the same result.
• The phone OS is up to date.
• Powered down the iPhone and powered down the watch, reconnected and tried again and I get the same result.
• Watch is always on the charger.
• Can't see anything on the watch or iPhone to delete.

A total mystery. Can anyone help?

Thanks,

pbennett49