Failed polygraph question?

I have NEVER taken or even tried illegal drugs or substances and failed the question twice. What should I do or if i can request for another poly? I applied for Prince William County Police Dept. Can someone please give me some good advice. I shoplifted twice and told the examiner so theres no reason for me lie about it and i akways thought that i would fail that question but i've never ever used or even tried any drugs, i'm so upset...