When you place a vehicle in business for the first time (and this is probably the first time, since you could not have claimed it for a regular job since 2018) your basis is the purchase price, or the fair market value at the time it is placed in service, whichever is lower.
That doesn't help explain where the error is coming from, and I can't see all your entries so I can't trouble-shoot from here. But @Critter-3 is right, for a used vehicle you are probably much better off using the standard mileage method, and that should not require providing a basis at all.
I suppose it's possible that if you placed the vehicle in service for your W-2 work in 2017 using a non-standard expense method, you might not be allowed to use the standard mileage rate now, but we would need more information to help you now.
