How to delete a user when you type "Username" and the Block user and Delete user buttons remain grey

How to delete a user when you type “Username” and the Block user and Delete user buttons remain grey

When I attempt to delete a user, I am prompted to enter their name into a dialog box in order to select the “Block user” or “Delete user” buttons. Both are greyed out.

After entering the text, the buttons remain greyed out. I would expect it to enable the buttons to delete or block at this point.

What else can I do?

Cheers,
Joe