If a renewal or new claim for DLA is refused, the Decision Maker dealing with your case has to provide you with written reasons why your claim failed in an understandable form.
If a claim for DLA fails, we always advise claimants to appeal rather than ask for their claim to be looked at again ( Called a 'reconsideration' by the DWP).
You can download an appeal form here
Appeal against a benefit decision (leaflet GL24)