If you receive one of the below messages, this means that an invitation for this parent or teacher has already been sent out for your centre.
This can occur if you are trying to invite the same family member to multiple children / siblings. They will need to accept their invitation before you can link them to their other children.
Parent/Family Invite Message
Teacher Invite Message
If you cannot see them on your teacher page or they are showing as Pending under the child's profile this means they have not accepted their invite.