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It depends on what year you served, if it was before 1979 it only has to be 180 days served as long as your DD214 states under honorable conditions, if after that date it has to be 2 years served. Once you got out did you have any other service (Reserves)?
Also, you mean to say that your COE was denied not your loan, correct?
what does the dd214 say?
do you have va loan 'eligibility'?
if not you need to look at other options for your loan
good luck