I tried to join the 'Rookie Cup' races yesterday, and again today. I have all the required DLC. I am correctly enrolled in the series, and I registered for the race each time. I got a screen with the briefing, telling me that the race would load and start once the timer ran down. However, once the timer got to zero, nothing happened for a minute or so, then I got a message saying 'Too late'. And that was it. No race. It's happened a few times now, and I've basically given up in frustration. Although I've been sim racing for a couple of years, this is the first time I have tried to race online. it's not an experience I'm enjoying so far... Am I doing something wrong? If so, it shouldn't be this difficult and the system needs sorting out.
Check your computer internal time, they can drift with time and this cause trouble with CS system. Check with things like this: https://time.is/ then change your clock settings.