I joined the 3R hilly race yesrerday. Although it said there were 120 racers, i only saw me at the start and all through the race. What did i do wrong?
Sounds like you had/have a bad network connection to the Zwift servers. When all the riders suddenly disappear or in your case never appear, it is likely to be your network connection.
Double check your internet connection. Also make sure you completely close/shutdown/force-quit Zwift and the Companion app after each session.