I need to remove or update an existing administrator but when I try to do so I see this error:
"You are not currently authorized to perform the operation or view the page that you have selected. If you have not yet logged in, please do so now. If you feel that you have received this message in error, please contact your site administrator."
This indicates that the administrator you are trying to edit/remove has a higher permission set than you do. For example, if you are a subadmin, you can not edit or remove a site admin.