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If it was DTI that caused the denial, then getting your score up probably won't help. You need to get some debt down. What is your DTI percentage? I think FHA does not really do anything much over about 31-43% but have seen some posts here with people saying they have done them over 50%. Not sure whether there where other compensating factors such as reserves, down payment size, etc.. that allowed a higher DTI
See what FHA.com says about it here and how to calculate DTI if you don't know what your's is.
https://www.fha.com/fha_requirements_debt