Ratings will start to display on your graph on the dashboard when you have completed 10+ clean time trial sessions (in iRacing, Assetto Corsa Competizione, AC EVO, AMS2, LMU, Forza Motorsport, F1 25, F1 24, F1 23, F1 22, F1 2021 or F1 2020).
If you are using Assetto Corsa, then these 10+ sessions also have to be completed on track/car combinations that have had enough other drivers driving the combo. Therefore, in order to see the ratings, it would be advisable to first drive Kunos cars and tracks.
Have patience, your rating will appear soon 😀