I have just been setting up my latest raspberry PI and brick pi card.
I could get the motor test example to work although only one motor would work (A) until I changed direction then both A and D would work,
However the car example would not work. After spotting my deliberate mistake of not changing it to use D instead of A it still would not work.
Then I noticed that the car example does not enable the motors. Modifying scratch to enable motor A and D when green flag was clicked seem to fix it, but then I hit another problem, see my general post on " think I have just killed my PI and BrickPI"