I live in Ohio and work in PA for the past 8 years. I have never filed PA taxes before. Why do i have a tax due this year?

In the personal info section, when it asks if you made money in another state, answer NO, per the reciprocal state instructions, on that page. This will prevent TurboTax from thinking you need to file a PA return.

Ohio has a reciprocal agreement, on wages,  with all neighboring states. No state taxes are withheld or due and you do not normally need to file a return for the other state (MI, PA, KY, WV, IN). But OH will tax you on your other state income.

If PA taxes are mistakenly withheld, you then have to file a return, for the other state, to get a refund. OH will not give you a credit.