You told the program that you DID sell it, weather you realize it or not. It's apparent you did *something* with the vehicle in 2019. My guess would be that you selected the option for "I stopped using this vehicle in 2019", If you selected that option, then you would have been presented a screen titled "Special handling required?". If you selected NO on that screen, then you sold the vehicle and the program will insist that you enter sales data and will not let you e-file until you enter sales data, or go back and change "Special handling required?" to YES.
