I am trying to convert a User Mailbox in our Onsite Exchange 2013 server to a Shared Mailbox. All research I have done online simply states to click on the user's name to highlight it in the Exchange Control Panel and then use the right-side menu and find "Convert to Shared Mailbox", however when I do this, the convert to shared mailbox does not appear as an option in the menu. Here is what I see for the menu on the given user: