Either you did not meet the requirements or you do not have a tax liability.
Requirements:
- exterior doors, windows and skylights, insulation materials or systems, and air sealing materials or systems: the home must be located in the United States and must be owned and used by the taxpayer as the taxpayer's principal residence
- Exterior residential windows or skylights must meet the ENERGY STAR Most Efficient criteria to be eligible for the 25C Federal Tax Credit.
Tax liability:
This credit is nonrefundable, which means the credit amount you receive will not exceed the amount of tax you owe. Therefore, there is no refund.
Federal Tax Credits for Energy Efficiency states:
Example: If you owed $375 in taxes, but you received a nonrefundable credit of $500, the tax you owed was reduced to zero, and the remaining $125 was lost. You would not receive a refund for the remaining $125.
Reference: windows