Work in NY, live in NJ: Adjusted credit for taxes paid to NY, now I owe NJ over $3,000?

I work in NY, and live in NJ. I used Turbotax to file my 2017 taxes (federal and state). Now (3 years later!), I get a letter from NJ dept of treasury that I owe them over $3,000! The letter says that "we adjusted the credit for income taxes paid to New York"... One of the reasons that I used Turbotax is to avoid these complicated tax filings... What could have gone wrong? 

Thanks for any help!