This error means that the user has registered with different details to those held in ParentMail.
To make sure the parent is connected to the school:
- Search for, then select the required parent.
- Remove, then re-add, the relationship to their child(ren). Please see this article for instructions.
- Resend them a registration link for them to connect to your school.
- The parent user should then follow the instructions to reconnect to your school.