unable to activate update required

Your iPhone likely needs service. (the only way to solve this issue most likely)

It might be covered under:

iPhone 7 Repair Program for "No Service" Issues - Apple Support

Depending on what model you gave.

In any case contact apple to check your repair options:

Contact Apple for support and service - Apple Support

Good luck!

Agree with Androish, I’d contact Apple Support for that error, especially after restoring from recovery mode and the error persists. Of course many stores are closed now but there are options to send to Apple by mail, and other stores (Authorized Apple Service Providers), that can help as well. The Apple Support app, I’ve found to be the easiest to do do that, hope that helps!

Link to the app:

https://apps.apple.com/us/app/apple-support/id1130498044