[Handy Hanafiah]

I am experiencing the same problem, I tried to join the Oreca race in Road America and game crashed everytime I tried to join, CM or Vanilla AC did not make any difference. I checked the steam ID thing and it's ok.
Right now I see that 8 of 9 drivers registered could not join the server, just one got connected.

Same thing happen on Tuesday, but luckily admin is online and quickly resolve the issue.

Back to oreca, it's seem only 2 people manage to race (based from standing leaderboard), but the points of that race didn't appear, so I assume that race is cancelled or counted as unofficial, so if you chase the championship you miss almost nothing.

Aside from something obvious like internet issue, server issue(very rare btw), unmatched steamid, outdated mods etc, sometime SRS skin transfer can cause crash on some tracks, in my case almost every Americans track (mod) keep crashes if I enable SRS skin app.