Error 403 sounds like it’s a response from server, but maybe not? I’ve found that with VRCX you can refresh count of a specific instance. Maybe see where that gets you? Whenever VRChats in game list is acting up, I’ve usually had good results inviting myself via website or VRCX.
If they actually stop caching user counts, that could be very entertaining, maybe they could make it like a game server browser from the 1990s. Hit refresh and then wait as your computer checks in with every server on the planet individually
Actually that’d make a great gimmick for April fool’s
But since we’re in the future, they need to make tweaks to how that caching works.