I applaud the OP for looking for help and trying to find a resolution. Even if my prior posts are leaning towards suggesting he discontinue signing up to GM since I do not see enough details to know.how much if the problem is the player or GM.
I think everyone can understand cancellation due to family emergency, work, and sickness. I still do not condone signing up to GM before finding a solution for the problem at hand.
I think it would be terrible for a player to spend $20-$70 on a convention badge, maybe hotel cost also, then be told they are not allowed at the table due to prior events the week before. Tell the player a problem exits before they undergo these costs. Even smaller costs at a single game day event. That includes buying food at the hosting spot or miniatures/cards at a game shop. Even a convention may only have 2 or 3 PFS games a slot but the others may have already been played or out if tier(pregens should only be used for people who never built a PC). The con may feature other.games, but they might nit be what justified the cost of that con badge/hotel/travel/weekend food in the first place. On the other hand, if a player shows up to a con and acts there in a fashion worthy if being banned, tough luck.on those expenses, and that player, but warn a player first if the problem was known before hand.