i encountered the same issue and found the cause was due to another tax credit taken from installing solar on my house. the rules of the "Alternative Vehicle Refueling Property Credit" limit the benefit based on other credits taken in the same year... wish i had known that before i had a car charger installed in December.
to verify the calculation is correct, you can click on the "Forms" link in the upper right of TurboTax window (i'm using installed software, not web based version), then select "Form 8911." line 14 is the total tax owed from Form 1040. that is reduced by values in 15a and 15b. for me, the solar tax credit appears on 15b. to see where the value in 15b came from, go to the "Schedule 3" form and look at lines 2-6.
