There are a few reasons drivers end up as 'Red Light' event status:
Most common - If you are a Guest member, you are sorted below the supporting members, who receive priority signup privileges. This is true all the way up to the time of the race. You can be bumped out of Green-light status even in the final minutes before a race. It is your responsibility to check your status, and leave the server if required, even if you were issued the race password prior.
Occasional - You may have failed to attend previous events which you registered to attend. "No-shows" will cause your entry to be sorted lower in the list. (Guests only)
Occasional - Newer members of Race2Play are given enhanced-opportunity to participate. Long-term Guest members may find themselves on red-light status as newer members slot ahead.
Rare - Your supporting membership may have expired, putting you to the mercy of the above stated cases.