Here’s what causes it: If a co-author already exists in the system (probably because another submitter submitted an abstract and added this co-author), the system does not allow the submitter to make any changes to the co-author’s profile.
So, if submitter adds a co-author who already have a profile in the system (either because they have created an account previously or have been added from another abstract submitted earlier), the submitter would be able to add them to her abstract but couldnt update their profile.
Why the system does it: The reason system does not allow submitter to add information about a co-author who exists in the system is to ensure data integrity i.e. to prevent any submitter from being able to edit co-author’s profile information they have added on their own.
Resolution: An admin can always update the info from the backend. Alternatively, co-authors can update their information by going to Update profile button in the user dashboard menu.