You don't owe MD taxes if your income from MD consists solely of W-2 earnings.
MD and PA have tax reciprocity for W-2 earnings. That means that if you work in one of those states and live in the other, you only have to pay taxes in your state of residence. If that's your situation, answer No in the My Info section to the question about having income from another state.
**Answers are correct to the best of my ability but do not constitute tax or legal advice.