Unable to restore iPhone - iPhone disabled

My child has iPhone SE. She disabled passcode a few days go. Today she tried to turn on the passcode function but was not prompted to generate a new code. Instead iPhone requested to enter passcode. She tried to enter old passcode but it doesn't work, as if it was wrong passcode.

Now we are trying to restore the iPhone by connecting it to a computer. We follow the procedures but the recovery sw does not get downloaded and after a while iPhone switches on in disabled mode. We tried several times and the outcome is the same. How can we solve this problem?

Thank you, Mike.