I am active duty Military stationed in Hawaii. Last year I owed $0 in state taxes. This year I owe almost $2,000. Why is that?

It depends on the laws of your state home of record.  First, go back and check your entries in "My Info" to be sure you have indicated that your resident state is your home of record state.  Next return to the "Wages and Income" W2 topic to verify your entries there including the follow on question (Uncommon Situations) where you need to indicate the W2 is "Active Duty Military Pay."  

Many states do not tax your military pay if you are stationed outside of that state but some do .  Here is a link to  check on the laws of your resident state.  

If your resident state does tax your military pay then check for state withholding in boxes 15-20 on your military W2.  If there is none you will need to have withholding adjusted through your finance office.   

Your active duty military pay is not taxable in HI if that is not your home of record.  So if active duty pay is all you have and your home of record is not HI, then you did not have any HI source income and do not need to file in HI.