You cannot use past perfect because it usually states:
--an action completed before a certain point in the past:
e.g.When I arrived , he had just left
-- an action completed in an unspecified time before a certain point in the past:
She had lost her car keys so she had to take a taxi.
-- in Indirect Speech:
"She left ten minutes ago"
He told me that she had left ten minutes before.
- For Teachers