My Maryland state taxes say I must enter the institution where I teach. I'm not a teacher. Why does it think I'm teacher and why won't it let me leave it blank?

There may have been an errant entry earlier in the interview.  Check by trying this:

1. If you’re on the Hi TurboTax Client, let's keep working on your taxes! screen, click the dropdown to the right of Deductions & Credits, and select Review/Edit.  Otherwise, select Federal in the left pane, then Deductions & Credits in the banner
2. Scroll down and select Show more to the right of Employment Expenses
3. If there’s a Start button to the right of Teacher (Educator) Expenses, don’t select it; this didsn’t cause the issue you’re experiencing.  If there’s a Revisit button, select it 
4. Remove any unnecessary information on the subsequent screens

If this doesn’t solve your issue, please respond back.