Thanks for letting me know, and I’m sorry—I may not have made the controls clear. The cars wait at the starting line during the countdown. In solo mode, hold the Up Arrow key after “START!” to accelerate. If you have a chance, could you please try that? I’d really appreciate it!
Ha, beat it! A little messy, but I think I finally got the idea! Turns out there's a cutscene at the start, and I probably ran into a bug last time, since all the cars were stuck at the starting line. This time, I waited for them to start moving before hitting the accelerator, and it worked for me XD