I am told that I cannot efile my state taxes because "return claims a Solar and Wind Energy credit carryover." I typed 0's when prompted about this credit. How to fix?

Assuming that you're referring to the New York credit, to delete any erroneous data in the state interview portion of TurboTax Online:

1. Open TurboTax Online
2. Select Tax Home in the left pane
3. On the  Hi, let's keep working on your taxes! screen, select the dropdown on the right side of the State Taxes box, then select Start, Continue, or Pick up where you left off
4. Select  Edit to the right of New York
5. Proceed through the state interview until you come to the Take a look at New York credits and taxes screen.
6. Scroll down to Other Tax Credits, and select Start or Update to the right of Nonrefundable Credits
7. On the Nonrefundable Credits page, delete any entry next to Solar and Wind Energy Credit Carryover
8. Select Continue
9. On the Take a look at New York credits and taxes screen, select Continue

If this isn't what you're referring to, feel free to post back.