iOS 14.8 Software Update Don’t Work

Go to settings/General/iPhone storage. How much free storage do you have? You need at least twice the size of the update. And look for an update partial download and delete it if you find one.

also, for automatic update the phone must be plugged in.

Can you post a screenshot of the entire screen, not just that message?

It was set to automatic updates. As it didn’t update automatically I set it to manual. This is my screenshot;

This is the same result with the automatic updates on;