When an admin is adding a reviewer (or invitee, etc.) that person has to click on "save reviewer" and then on "save application." Just clicking "save application" does not save the reviewer even if all necessary information has been added. This is confusing - there should be one save button that takes care of everything even if someone hasn't clicked on "save reviewer."
I have several times clicked save application instead, and had to go back and redo my work.