"Could not Sign In" to iCloud

Dear all,

message "Could not Sign In, there was a problem connecting with the server"

iPhone 7 cannot sign in to iCloud. The connection to the Apple ID works well from the phone, and the connection to the iCloud ID works well from a web-browser or from another iPhone.

I've tried to remove the device from the account list, I've tried to flush the iPhone settings as well as the network settings. Did not work.

I've followed the different steps from the Knowlege Base https://support.apple.com/en-us/HT203512

Did not work.

Anyone has a clue / guidelines?

thank you,