Stars no showing in Google search listings.

Just wondering if I am missing a setting somewhere or if this is from Google. Other sites in organic search results show:
the number of stars Rating:4.2 – 56 reviews (Some have a price range after this)

On our site this is shown:
Aggregate Review : All Reviews – 4.9 out of 5, 5 votes, 5 reviews (No nie little yellow stars at the front ?? )

Can anyone suggest why this may be the case?

Thanks!