Hi!
The error message hints at the problem. If you set min z to 0.003, there is an infinitesimal gap between the wheels of the car and the bottom face of the flow region.
Having a closer look:
It’s a roughly 3e-7m gap, which is not desired for CFD. If you change z slightly, the gap doesn’t exist anymore and the flow region is created successfully.
Just as an example, here’s a thread where the user faced a similar problem: Velocity field is diverging at a point - #2 by Ricardopg
Cheers