What happens if you sign up to run an event, but not enough people sign up for it? It doesn't give the answer in the event host policy. I assume your event just doesn't run, and you can't collect the tickets, so nobody is charged. Like your event requires 10 people minimum, but you only get seven. Thirty minutes into your event time, you just don't get the other three people.
You'll want to double-check the EHP and the submission videos again - everyone is charged when they buy ticket to the event, the charge isn't held until the event actually fires off.
If you don't get fewer that your submitted minimum number of players when you need to start your events, you will first want to try to recruit players from the "looking for players" Discord channel and see if you can adapt your event in any way to still work, just in case. If neither of those pan out and you just can't get enough players, then you need to notify Gen Con that the event has been canceled so that players can request a refund from customer service.
Senior Event & Program Manager
Gen Con LLC
Okay, so the other question is, what happens if zero people sign up for my event? One of the events I'm hosting, I can't guarantee I will get any sign-ups cause it ain't an organized play of any kind even though it is a dungeons and dragons game. Very few D&D 5e players, pathfinder players and starfinder players will play if there ain't organized credit involved. Does it count as a cancelled event against me if I get zero sign-ups?
First, I wouldn't worry about non-organized play games, honestly. The official organized play events at the convention are big, but there are still thousands of people play D&D in general. At the scale of a single game, you don't really need to worry. Focus on making your events and description as interesting and evocative as you can and you can still find players.
Second, if you don't have enough players for your event and need to cancel it, you aren't punished for that. though if it's a pattern across multiple events that should inform what kind of events you want to schedule in the future.