Why would I get mileage deduction for 1 car but not the other? Got $250 for 450 miles on new car. Says $2.5K for 4K miles on old car, but disappears when click "continue"

I put that I stopped using this car 11/20/2020. It initially comes up "Kaching" that I get a $2500 mileage deduction, and my tax due total goes down by $150. Then I hit "continue" and the $150 come back, and I'm told I don't get any deduction on that car. I don't get it.