Denied

I recently applied for an auto loan and got denied . I have a 672 credit score although I know it isn't good. And I my DTI is good but my credit age is about 2 years and I have about 5 open accounts . It was for 25k and I really had faith as some people had a lower score than me and had stated they gotten approved. Any suggestions? Because they told me it had something to do with something reported to my transunion.