NEVER delete a contact email and re-add, or delete a contact and re-add using previous email. Email address is the unique identifier for a proxy and cannot be changed or removed/re-added. If this has been done the only solution is to create a new contact with a different email. 

Helpful links

Student Questions

Parent Questions

Ask the student to follow the steps from document "How to Add Emergency Contacts and Third Party Proxy Access"

Make sure the student used the correct email address. If there is a typo, the student should remove you from Friends and Family, and
then redo the process (add to Friends and Family with the correct address, then manage permissions.) This will trigger the creation of a new account with the
correct email address.