None of the motors or sensors are working

That’s exactly the point why I am writing “Quick Guides” about these kinds of hobby programming things -
perhaps you might have a look at my Quick Guide to BrickPi3 and C++

PS,
over all it takes about 30 minutes to install Raspbian by NOOBS on a new SD card from the scratch (automized) and just another 10 minutes to make all the BrickPi3 things work, about drivers, firrmware , and everything!