This is usually caused by the User having a Student Role (Student, Past Student, Candidate, Past Candidate). This will block some changes from happening in School Website as the "Student" Role is more restrictive. For this to work correctly, either impersonate another Page Manager that does not have the "Student" Role, or remove the "Student" Role from the User that is trying to make the change. We are looking into options to possibly change this in the future.