Assuming that the drift scores are showing when driving and completing a lap, then could be a $defaulttopcar issue - use the search facility and look up $defaulttopcar and read results.
Try !drf and !drf xrt or !drf <your_car_type> - if nothing shows under !drf only, but shows when you also add your car type, then it is a $defaulttopcar issue.
Same will happen with !top command.
If you're racing round a layout you've made then you need to place a finish line (SHIFT U, etc), so that lapper knows that lap is complete.