Shared users can't be edited in the application
When you try to edit a user in your application, you receive the following message:
Shared user can only be changed by himself/herself
Shared users that have the _WebLogin to multiple applications can only be edited by the user himself/herself.
Use impersonation from Site Admin to log in as the user to the application, and then make the changes you want to do.
Remove the user from any role that has _WebLogin enabled from Roles in the Admin menu.