I'm still having this issue with the x64 version. I've re-installed, deleted my user folder, reinstalled gpu drivers, reset modem, reset router. Before this issue started of course nothing on my system, or network had changed
The 64bit title doesn't launch, it sits at a black screen then eventually times out and gives the 503 error. It started the same time others got this error but has never worked when maintenance was completed or the updates. Assuming the logs are in the folder \Documents\My Games\SimBin\RaceRoom Racing Experience\UserData I first launched the 64bit and let it do its time out then exited. Then launched in 32bit where it worked correctly, went to my user portal then exited. Please advise if there are different logs for troubleshooting.
So after moving to a different drive I launched the title, it made me install some launcher program and x64 now works correctly.